Thank you for all these suggestions. The FS Langkawi looks lovely, and the beach villa would be perfect.

Amanpulo is certainly up there - and remarkably good value on our dates. The hotel have said they'd be happy to squeeze us into a casita. Given a villa would be out of our price range, does anyone who has actually been there think it would be too much of a squeeze?

One other place that has grabbed our attention is Costa Rica. Any experiences of the hotels there? FS or Andaz Papagayo? Others?

Once again thank you for the great suggestions.