Hi geespot,
Cheapest I've seen is 435 + tax to bkk on 2/7/04 Qatar Airways
Direct is 480 + tax with Eva. Both with
www.flightlinker.com
Phuket Air fly from Gatwick on thur, sat & sun 425 + tax but can't get a date free on their website in july
As a last resort I've used
www.airtravelguide.com for emergency short notice travel and they've always got me there.
Been a long, bumpy ride sometimes, though.
Good luck...