Restoring aircraft types in non-country of origin

Cees, I´m afraid your question is a bit difficault to answer, but I´ll try my best. I´m by no means an expert, but this is how I understand the rules at the moment.
Lets start with an aircraft of british origins being restored in another country. In that case, two basic scenarios exist.
If the aircraft has a recognized Design Authority (DA) in the UK (for example dH Support for most dH types), any and all change in the basic design must be approved by the DA holder. That for example applies to substitution of BA hardware with AN hardware. If the DA holder approves such a change, I can see no reason for the CAA to refuse import of such an aircraft to the UK with full registration without question. The aircraft must furthermore be registered as Normal Category aircraft (if flown before export to the UK) in it´s country of registration if the CAA is to approve it on the register.
The next scenario is a british design restored in a foreigin country, but one that has no DA in the UK. In that case, the aircraft has to be restored to the original standard (all hardware and work practices), and has to be registered as Normal Category aircraft in it´s country of registration if it is issued with a an Airworthiness Certificate.
Reason for this emphisis on Normal Category registration in it´s country of restoration, is the fact that experiment category (or permit to fly) is not an internationally recognized restoration/maintainance standard, and so, will most probably not be recognized in it´s country of import. Even getting an FAA Experimental Category aircraft, that is not supported by the LAA, onto the UK Permit to Fly register is impossible. Just ask Hairyplane about his Klemm:o

If you have an aircraft originally built in a foreigin country, you can import it into another country (UK), as long as it´s restoration was done to the originating country´s standards for a Normal Category of Airworthiness. It might, however, end up on the receiving country´s experimental (or permit to fly) register, if the type has not got a valid ICAO type certificate.

Lets take some examples here. I´m restoring a Miles Gemini in Iceland. I´m restoring it to original specs, but there are two roads open to me. I can register it in the Icelandic Experimental Category, in which case, it will not be accepted onto the UK register again unless it is taken to pieces and the build quality checked against the original specs or the DA´s approvals for changes to the original specs. As the aircraft is already done to original specs, I could register it in the Normal Category, with mechanics sign off for all stages of the restoration. In that case the UK CAA will probably accept the aircraft without questions onto the Normal Category in the UK.
Take another example. An american warbird is restored in the US. It is done to FAA standards for Normal Category aircraft. The UK will accept such an aircraft onto the register either as a Normal Category, or a Permit to Fly, and that is the devil in the detail, as it will probably take a few negotiating rounds with the CAA (with all the paperwork at hand) to establish into which category the aircraft will fall. If this same aircraft, restored to the same standards, would have been FAA experimental category registered, there would be no hope to get it onto the register (without some very good negotiating tactick on behalf of the new owner).

This is just how I understand the basic rules. I´m open for correction on the basics. If I´ve got something seriously wrong, someone in the know please correct me.
Anyway, come 28th of September, all will change when the new EU rules come into play. I must admit that I´ve not read them well enough to say what changes will come at that time, but I suspect they will be considerable, and maybe not all of them for the benifit of classic aircraft.

All the best,
Sigurjón

IME any Brit warbird restored in the US will be dripping with AN/NAS hardware, including the rivets & I know some (non-critical) BA threads on Merlins are retapped to US thread sizes.