Thanks all, I love this forum!! I think Rayavadee sounds like it will fit the bill. The scenery looks stunning. The only thing which I was hesitant about is that I've read some reviews which suggest that (a) the food is mediocre and (b) the villas are a little dated. Dated doesn't worry me too much if they still have a great atmosphere - I don't need a minimalist masterpiece, but there's a difference if the rooms are worn or shabby.

FS Langkawi also a good suggestion but I'd prefer to be in Thailand as I have family there so will be doing some other travel too.