I think that it is sacrilege that the Battle of Britain Hall is to be split up, regardless of the short duration of the battle, it was a pivotal point in British history and should always be commemorated. I think that the hall could do with a revamp, possibly opening up the end with a whole glass wall as per the Sunderland end. I agree that the information boards could have much more information on them and while i personally hate interactive displays, perhaps they could contain more relevant information.
As for making everything more appealing to Joe public, surely if you are visiting an aviation museum you are going to see the airframes and associated displays, if you want to mess around on a computer screen, you can do that at home.
The mezzanine floor is an attraction that is too often closed which annoys me because i like this part of the display very much, not only does it allow you to see the items on display and the sector control room, but it also allows you to see the aircraft from on high. I used to love the galleries in the main hall but sadly these have all now gone.
I think if they introduced some flying clothing displays along with the aircraft, this would be very interesting and appealing, to be able to see the type of equipment worn by the aircrew of that type particular aircraft as has been done with the Defiant air gunner. I must confess a certain bias regarding this as i am a flying clothing collector.
My friends and i have noticed what appears to us, a distinct dumbing down in aviation museums to appeal i imagine to people with only a passing interest in the subject. I appreciate that it must be a fine balancing act to try to appeal to as wide an audience as possible but personally i don`t want to see a lot of unrelated items shown in an attempt to appeal to a younger market. There is a display case at Duxford that contains among other items, a Typhoon control column at one end and a Snakes on a Plane DVD at the other, go figure !
One must also consider when updating/upgrading a museum that change is not always for the better, one only has to look at the massive amount of money spent on the IWM at Lambeth which was in my and my friends opinions, completely ruined.
On a slightly different note, the open cockpit evening they had in the Battle of Britain hall at Hendon was marvellous, it was great to be able to get really close to the aircraft and take pictures which at any other time would be impossible, i was only surprised by the lack of numbers there, two hundred by our estimation which considering the event was a one off which is never to be repeated seemed a very low turn out.

How much are the tickets ?

While it doesn`t conform to the standard kings crown shape, it is often seen on wartime equipment, it is just a more stylised version. My friends and I all have equipment in our collections with this type of crown on. It is seen on all sorts of equipment from Mae West`s to Harmessuits, parachute equipment and furniture to name but a few.

I can`t really help you re the different types of vent you have seen but below is an advert for Luxor 8`s and the vent is the same as your picture above. Luxor made goggles for both the military and also for commercial aviation and so there might have been subtle differences but there isn`t any definitive information on the different types of Luxors available. I used to have a pair of Luxor 8`s but I sold them a long time ago and so can`t compare them for you. I`m sorry I can`t be of any more help but information on this subject is a bit sketchy to say the least.

It should be worth more as it`s rarer, but time will tell.

Well it went for £160, so pretty strong bidding I`d say.