I just spent the winter at the RNSYS, and the arm froze thick enough to make
dinghy access difficult at times. If they're working on land, try armdale YC, or RNSYS.
If not wanting a marina, and aren't working on land, then near the rotary works, or Dartmouth, near the yacht club.
If ice isn't an issue, then Lunenburg would be my second choice.
Cheers.
Paul.