Don't know what the current state of the restaurant is at Sandown, it was razed to the ground by arsonists a while ago. Bembridge on the IOW has more modest restaurant but do take the walk into the village and go to the Crab & Lobster, a great 'destination' Sunday lunch pub and restaurant. Highly recommended.
Of course you could always come round the zone to Denham and go to Biggles, very nice but rather pricy restaurant, just by the Control Tower. Both the aerodrome and restaurant are strictly PPR.
Cheers,
TheOddOne