If you have a sporty car you could book it into
Plans Motorsport for some work, or even just an oil change - their workshop is on the Dunsfold Aerodrome site, and when I was there last it was easy to see many of the aircraft on site.
I'm sure there are other businesses on the site that you could have a legitimate reason to visit, as well
Of course, the Casino Royale lot might still frown on you taking photographs.