A plug here for my local lake, Poole Park Lake in sunny (occasionally!) Poole down here in Dorset, next to Bournemouth and even closer to Westbourne Models. Poole Radio Yacht club use it regularly (though not exclusively) and they also have a fair sized scale section. I'm not a member of the club, but they seem a friendly bunch...except, perhaps, when they're racing!
The Boating Lake section of the lake is a good size, has free parking right next to it, though limited spaces, and there's a cafe and toilets not far away (coupla hundred yards). The lake has all round access, no reeds and is concrete sided so access is pretty good. It is not very deep (18"?) so bigger yachts with long keels may get 'bogged down'. It is salt water though and the council do drain it from time to time, usually early spring I think.
Mike