Thanks for all the advice everyone, I ended up going to Cairn Curran Reservoir, as it was nearby someone selling second hand gear.
Had a great time, although the lack of wind meant that I didn't really get anywhere. The other drawback, the sailing club there has a great grassed area to rig up, but when the dam is at only 35%, it's a 100m walk to the water! That said, it was a great spot, and I'll definitely return.
The other great news is that I'm now the owner of a Starboard Carve 151, with a few sails! (sorry, only got a pic of the Ten Cate)
Cheers, Simon