Thanks everyone. I spent the weekend trawling through Hayes & Jarvis/Barefoot Traveller brochures and I think I have myself a shortlist based on your comments on this thread (I'm a strong believer in personal testimonials) and info from the brochures.
So I'm thinking it will either be Cayman Islands, Tobago, Turks & Caicos or Curacao. All of these will be fine to visit in November weather-wise and all have pretty good diving apparently...
Just on further question - all these brochures are bloody expensive so I'd be interested to know whether you guys book full-on package deals/all-inclusives which include the diving or whether you just book the holiday, get there and mosey on down to the local dive centre to strike a deal
?!
I can't stand the thought on doing a Sandals but actually it makes the diving prices quite reasonable. Oh god, decisions decisions!