My wife and I have been. I can't recall the cost but it wasn't much. It's a brilliant museum and as there will probably only be a few other visitors with you, you get very personal service. The Trident and Comet are there plus the wonderful Connie.... and many other very interesting aircraft - Dak, Gugnunc, Dragon to name but a few.
Give it a whirl. Guess you realise that you have to book in advance..