It really depends when you are going, ive seen low fare at around £ 370 inc tax with Ethiad, Royal Jordanian & Turkish Airlines.
If you planning to go over Christmas/New Year or any of the Kids holidays forget the chance of a low fare. Direct flights from London with Thai, BA, Qantas and EVA air usually work out about the same fare from £450 to £800 inc tax again depending on date. You may get some cheapish fares with some of the former soviet state airlines like Turkmenistan Airlines. Try expedia, lastmin, thomas cook, travelmood, airline network etc. Good luck