They have an option where you can sit in one of the Spitfires but that needs to be pre-booked I think. I noticed it when I was there a few months ago. Don't miss the Grahame-White hangar, including G-W's office upstairs. In the main halls there are a few displays in various places (such as the medal groups from various airmen) that can be missed when you wander around from aircraft to aircraft but if you take your time you'll have a great day.