Travelling direct from the UK to Kuala Lumpur has recently become 50% cheaper.
Air Asia,the region's leading budget airline fly the route in a no-frills Airbus for about RM 1,800( 300 Sterling) return as opposed to MAS charging RM 3,800 (650 Sterling) You get what you pay for and with the Air Asia flight you have to pay extra for everything including blanket,meals,water and mediocre entertainment.
On the plus side it's cheap.On the minus side,well if you get a day-flight it could well be the most boring and miserable 13 hours you'll ever spend.The seats recline all of 10 degrees and there's nothing to look at unless you want to stare at the not-unattractive cabin crew or gaze out of the window and guess where you are.
The food is inadequate and bland,best to sneak-on your own (officially not allowed) and it's probably best to take your own entertainment along with you as well.
But,having said that,it's cheap and direct.The cabin crew are friendly and always happy to sell things to you.
MAS http://www.malaysianairlines.com.my/ sometimes offer good deals on their website to nearly match the above pricing and you get all the benefits of flying a scheduled service.
As alternatives you can also fly with a variety of the Gulf State's airlines (Emirates,Etihad,Qatar) all of whom offer competitive pricing with a stop-over to break-up the boredom of long-haul travel.