So the debate now seems to be
1) C2 as C1 lite
2) C2 as souped up C3
3) C2 dropped as being an unwarranted extra tier between C1 & C3

1) A stripped down C1 would still be expensive, but would leverage production costs from the other class, offer economies of scale in operations and support, and if we went for “fitted for but not with” on a grand scale costs could be kept reasonable. However it’d still be a lot of money for what seems to be a second line and Policing vessel. That said, it would leave the door open to later upgrades to bring it nearer C1 standards if needed later or in an emergency.
2) The RN looked at this with the Castle class OPV and concluded that costs rose massively when a OPV was given a genuine war weapons fit so that it approached frigate costs yet still fell far short of frigate capability. Even if the VT OPV was given a modest weapons and sensor fit (absolute minimum IMO would be a light callibre gun, a point defence SAM and some sort of ASW capability, possibly helicopter based rather than hull based with a reasonable sensor fit, now the Omani Navy are building just such a ship and it’ll probably serve them well, but it wouldn’t be anything like as useful as a stripped out austere frigate and wouldn’t have upgrade potential. Also there is the power and range question, fuel tanks don’t come cheap and neither does high speed, fit gas turbines and IEP instead of a 20kt or so diesel plant and it’s no longer looking a bargain.
3) Ditch C2, keep the OPV type C3 for Policing roles, build a basic but effective T23 replacement and keep the surface fleet down to two basic designs plus the C3 common hull MCM/OPV/Survey etc. design.

Personally, I vote for 3 as first choice, followed by 1 with option 2 of a beefed up militarised and armed OPV last.

AFAIK current planning is for a combined total of 18 C1 & C2 plus 8 C3, C3 is in addition to the surface combatants and is intended as a multi-role vessel to replace MCM, survey and OPV types eventually with a single class. C1 is supposed to be a first class ASW vessel and C2 an austere secondary warship for securing lines of communication and less threatening missions. In a way I think it is a regressive step from the older S2C2 concept of a very high capability multi-role destroyer and a much less ambitious GP frigate/corvette.
The argument for existing hulls is all about reducing risk and cost, and if the RN seriously wants the 18 C1 & C2 hulls they have to be ruthless in controlling costs, if the program goes out of control the way Astute did they could end up with half that number. At the moment the RN already operate or soon will operate two hulls that remain excellent and highly competitive, T23 and T45, so IMO it makes sense to use these as a starting point. Reading the requirement for C1 it does actually look very much like a T23 new generation, and using the hull as a starting point, with new machinery, a new lower RCS top side with a modern point defence SAM, light gun and fully optimised ASW sensor fit would give the RN a very good ASW vessel that they should be able to build for reasonable cost. My own argument would be that rather than design and build (or buy in a foreign design) a low end surface warship for C2, it’d make more sense to just continue the T45 program and upgrade the existing T45’s with ASuW capability, a new 155mm gun etc. and use the T23 replacement optimised ASW type as C1, and eliminate C2 as such, basically return to the older RN aim of a two tier force structure before the FSC project.
On the DDH, that is essentially a return to the through deck ASW cruiser, although it could be a much smaller vessel, it is often forgotten now that the light aircraft carriers were genuinely planned as ASW cruisers and that the often discussed concept was far from subterfuge to build carriers without the treasury noticing (even the treasury aren’t that dumb…) it is often claimed to be. A good idea, and a T45 derived hull would be a good approach, it does however have cost implications and implications for the balance of the fleet, and in some ways there is the question of what it would offer that an enlarged helideck and hangar on a more conventional design would offer, unless we look far into the future at the possibility of lightweight STOL/STOVL UAV operations.
On future MCM, I suspect fleet forward MCM may be best served by giving the surface fleet unmanned underwater vehicles for mine hunting, and possibly buying a few MCM Merlins and going down the US and Japanese airborne MCM route, as to build C3 as a fast MCM vessel is going to push prices through the roof and IMO it’d end up unaffordable, it would’nt just be increasing power, size would go up, because it’d be high value there’d be demands to increase mission profile and defensive systems, and from a technical point I suspect it’d be very expensive to combine speed and a good MCM hull.
I do think world navies need a good patrol/Police vessel. OK it may not be glamorous or win many promotions to flag rank, but counter-drug interdiction and anti-piracy patrols are a mission sorely under rated and essential to the security of global trade and domestic social and security issues. Yes, we can use large surface combatants, but why use vessels woth hundreds of millions, with large crews and huge running costs to do what a good sea going OPV worth a small fraction of the cost and with far far lower operating costs can do just as effectively. Such roles require an ongoing continuous long term presence, they’re not short term deployments, and that means the ships tasked with the role have to be affordable station ships.
Interesting debate, keep it going!!:)

My FSC;

-T45 derivative with ASuW/GP mission role (I’d like to retain PAAMS if possible)
-T23 replacement ASW frigate as described a few posts earlier
-the VT large OPV, possibly with a 57mm gun and RAM for drug interdiction, anti-piracy patrols, Police duties

Say, 8 T45’s, 4 ASuW T45 derivatives, 13 T23 follow on ASW frigates, for 25 major surface combatants, plus 8 large OPV’s for C3.

If either C1 or C2 is to be an ASW optimised vessel based on an existing hull then the T23 hull is probably better as a starting point, with the T45 hull being the basis of a ASuW/GP vessel, with or without PAAMS. For all the T23 hull isn’t in the first flush of youth the actual hull forms are a lot less subject to change and improvement than most other aspects of warship design (and it is surprising just what long timelines hull designs can have if you tace through their evolutionary developments) and the T23 was a thoroughbred ASW type fully optimised for low acoustic signatures and ASW work. Just my view. With RAM (or the possible ASRAAM based equivalent, there we go again, re-inventing the wheel) and a light gun with CIWS capability (eg. Bofors 57mm) it would be possible to build a pure ASW frigate with good self defence capability, actually very similar to T23.

The sad thing is that just as the UK was starting to formulate a realistic defence industrial-strategy with viable long term ambitions the defence procurement minister, one of the few genuinely pretty well respected men to have held a defence ministerial post in recent decades, has decided to go off motor racing. Now maybe he is genuine and just wants to drive racing cars (I can understand that) or maybe he’s fed up by the inane policies of the government and endless battles with the Treasury. I know which one I’d put my money on.

Whatever the production cost, it’s almost certain to be cheaper than paying to develop a new variant.

I agree, which is why I’m not sure the T45s need a long range missile. But if they do, Scalp Naval looks like the the best choice because of where they start from, i.e. already fitted with PAAMs & Sylver.

Which might be possible to meet by an off-the-shelf purchase of one of the plethora of existing anti-ship missiles which the latest incarnations of have been given land-attack capability.

All good points. I think one of the problems with European systems is that they tend to suffer from an economic nationalism in which the first choice is a local product, & the second choice is whatever the USA uses. As a result, the European products suffer from a lack of economies of scale, tend to be closely tailored to national requirements, & suffer the lack of upgrades you mention, because the national budget is stretched by the initial cost, & can’t cover long-term upgrades. Even the formation of multi-national firms such as MBDA & Thales haven’t ended this: individual countries buy from the local branch.

If European countries were more willing to buy each others products (please! No more multinational developments with workshare agreements based on orders & endless haggling over the split), pay firms in other European countries to develop weapons for them in the way in which many are happy to pay US firms to do, & less anxious to prop up local firms producing small numbers of everything, there’d probably be more world-class, competitive, European programmes.

I think we’re 90% in agreement on this one. If Scalp Naval makes most sense then I’d not complain about the T45’s getting it:)

My suspicion is that no8’s fate depends on the new SSBN program, the longer that gets delayed the more likely no8 is. The entire SSN/SSBN program at the moment seems orientated at design and construction skills retention, this requires a reasonably steady flow of work.

That is a good point, at the moment the MoD is acutely aware of how abandoning the Barrow-in-Furness skills base was disastrous for Astute as BAE had to virtually start from scratch at developing expertise they had let go a handful of years earlier, and they can’t afford the sort of screw ups of Astute to plague the SSBN replacement.

Very true, Indeed if one compares the T45 program to how Horizon turned out the RN is doing very well. The RN will at least have more T45’s than there will be Horizons built and each will be more capable. Of course 7 & 8 would nice as would another Astute.;)

The debate on Astute 8 is tied in with argument as to whether hull 8 should be an Astute or the lead boat of a follow on design. The Navy want 8 SSN’s, and given the decision to retain a SSBN force, the two CVF’s and the ARG in addition to intel and counter-sub roles 8 boats are going to be very tightly stretched. And the Trafalgar’s won’t last forever. I’m guessing if BAE offer a good price on Astute 8 the MoD may just go for it, but it does appear to be more than just a financial argument this time as the in service date for hull 8 is close to planning for the next design.