A broad thread.
The interest in Spitfires seems to be exponentially greater than any other aircraft; the BBMF are locked in a vicious cycle, and it's not their fault. At least they are preserving them! At one stage they were the only Hurricane operators in the world. That, at least is much better, and (quite an achievement) they are still operating 2 Hurris.
Defiant. One survivor, nailed to the ground by the RAF Museum. Missing the underside outer wing bolts and the tyres have no inner tubes. One 'full scale model' by the Boulton Paul Society in Wolves. Nice, but not a flyer!
Let's say you get the Defiant off the RAF Museum and under rebuild to fly. These days you can, with a lot of money go get P-51, Spitfire, Harvard (etc) parts from the nice suppliers, and the paperwork is not all 'new type'. The Defiant will all be new and nothing will be off the shelf. Think, it's a Merlin, but the coolant setup, fuel supply etc, while not really hard to redo, will be a one off...
If I recall correctly, the Canadian Mozzie project by the Zaleskys was good, but expensive. Projects are generally. There is one Mozzie being restored to fly in British Columbia, and a series new build production in N.Z. by a retired yacht designer builder. There's speculation about the Flighter Collection's example. Bigger = much more expensive + difficult.
Richard Melton has a Walrus kit for restoration, avaliable for sale. It's unique (only three other grounded survivors) but no-one's bought it. I'd love to see it fly, but those with money are apparently not bothered!
The LAST Blackburn Beverley is under threat of scapping at the closed Museum of Army Transport - despite interest and effort by some enthusiasts, led by the Yorkshire Air Museum, many enthusiasts have taken a 'so what' or 'it's big, difficult and I can't see the point' attitude.
Hope this adds a bit...
Cheers
James