Two small outfits worth a mention.
If you like Mosquito's there's a small museum dedicated to them near St'Albans. It's where the first one flew and very interesting. Small private museum but lots of info.
There's a small museum at Wycombe Air Park 30 miles west of London. Don't know what it's like but it seems to have had some money put in it recently.
Duxford is the one, Lots of live restoration work going on in many hangars. Don't miss it.