10 days is plenty- we have had been on a 7 day holiday before( but only to Hua Hin). We have gone with BA which is direct and with Emirates which is through Dubai- both took us in to BKK about 4pmish. YOu may want to take your Bangkok time then. I have actually just priced up flights to Phuket and they came out as £174 for both of us. Thai airways fly to Krabi and they come out as £226 for both. Actually for both airways it is possible to book an onward flight if you want to go directly to the resort and go to Bangkok at the end of the holiday. I think though that Thai airways use the old airport so it would not be so easy.
Alternatively, you could go to Hua Hin, which does not involve a flight. The journey is about 3 hours. I have actually done quick search yesterday for car prices and got £82 return but cheaper will be available- just haven't looked yet
Flights out of Bangkok often leave very late at night or early hours of the morning so you can have a complete day on the beach or by the pool before making your way back to Bangkok. IF your flight is late make sure you pay to keep your room on till 6pm to make the most of your holiday.
For Bangkok hotels have a look at our hotel reviews. For the moment, as this forum is new and still under construction, you will find reviews both in the Thailand section and the Far East. Pick a hotel that is near the skytrain as this will make a big difference to your holiday.
Welcome to HT by the way

In terms of maximising time on a short holiday I would aim for the flights that get into Bangkok early in the morning..say 6.30 am. If Bangkok is my first port of call, I've never had a problem getting checked in to my hotel room even though I've turned up earlyish in the morning...however I reckon you can get a better return on your available time by putting Bangkok at the end. I aim for a flight back to the UK around 8pm as this allows a full day in Bangkok, leaving the hotel around 4ish to get to the airport...its so much less tiring than the midnight - 1.30 in the morning flights where you're wrecked even before you get on the plane. Etihad has good flights that fit in with that scheduling....plus you get a 30kg luggage alowance good for all that shopping.

I've done Krabi a few times ..used AirAsia last time return flights cost us £50 pp

does Air Asia have a low luggage limit though Sunbear? I can travel light but not sure about 15kg

Air Asia does have a low limit of 15kg but we were over and never got charged. As we had the 30kg limit with Etihad its a good job we kept Bangkok to the end of the holiday. Anyway the extra baggage charge is not too horrendous. I think some of the other low-costs go to Krabi as well now.

thanks sunbear!