I don't know if this is the best place to put this, since it deals (mainly) with photographs (and some videos, other than I've found, I'm sure). But IWM does have photos and such of experimental and service type aircraft though the years. Of note is that they have a ton of World War II aircraft, including rare ones. Among the one's I've found are various photos (and a good video) of the de Havilland Hornet/Sea Hornet, the Hawker Fury/Sea Fury (including good photos of the Sabre powered variant), and the Supermarine Spiteful/Seafang. I'm thinking that IWM got their photos from the same place that the OP got them for the Air Ministry Pics thread.