Salsa Viva the Mexican in the High Street opposite the entrance for the Guildbourne Centre car park is nice. If the evening goes tits up you only have a 2 minute walk to your car and if things go well you can get a room around the corner in Steyne Gardens.
Big fan of Salsa Viva, but mexican food on a date might be dodgy. Although you could at least see how much of a 12" burrito she can fit in her mouth?
We've enjoyed Aqua (Italian) down Chapel Road the few times we've been there.
Crab Shack.
Best S&P squid around
Out of town, Sylvan Oak is well-regarded - http://www.sylvanoakfindon.co.uk
The Dining Room is very good indeed, and would be my first choice - http://www.the-dining-room.co.uk
Out of town, Sylvan Oak is well-regarded - http://www.sylvanoakfindon.co.uk
Montagues Tex Mex on Montague Street.
Fine food, massive portions and great value.
I concur on Sylvan Oak, if you're looking for a fairly expensive night out. Food great, it is quite a small little place though, but the service is fantastic (both my neighbours work there). You also have two nice pubs on hand for pre/post drinks.