Blimey, just noticed this got resurrected.
We went to Koh Samui in the end. Weather was great, just a few clouds and not too humid.
Unfortunately this happened on the way out clicky (which was the plane before ours
pretty scary start to the holiday!)
If anybody else is thinking of going, i'd highly recommend an afternoon at the Institute of Thai Culinary Arts. Delicious! And even though I'm a complete cooking thicko I can knock up a decent curry from scratch and it's actually edible
We stayed here, which was very nice - private pool, lovely villa etc.
One thing to watch though is being charged exorbitant prices (£10+ each) for tiny bottles of sun creme, aloe vera etc which we were assured multiple times were complimentary (and were for sale in shops across the road for £0.50 ish
). Pretty piss poor from a big hotel chain.
Koh Samui in general is lovely though, all in all highly recommended.
Edit: The Marizan caves posted above look amazing!