Re: Thanks for bringing back more memories!
The Flight exhibit on the top floor is pretty good (but less interesting for small people).
There's some one-of-a-kind exhibits in there, including Frank Wittle's first jet engine, and the Schneider Trophy, as in, the actual Schneider Trophy trophy itself, next to the S.6B that won it. There's the first Hawker P1127 (the prototype that lead to the Harrier) and Alcock and Brown's Vickers Vimy (first non-stop trans-Atlantic flight).
Basically, the more of a plane geek you are, the more fun you'll find it.