The trouble with blowers is that (a) high-power ones can actually damage your sensor, and (b) they're great at moving the dust around, but don't actually get rid of it all. Just about everything I've read about sensor cleaning tells you never to use a blower.
I've also heard some dodgy reports about sending the cameras back to the manufacturer for cleaning. They often come back just as dusty. I know at least one forum member who sent their camera in for maintenance and received it back in worse condition. I wouldn't send the camera off to the manufacturer unless absolutely necessary.
The method that was recommended to me and that I have found to be 100% sucessful is using a SensorSwipe -
link. It's a small flexible tool (which is actually made out of a rubber spatula) which you wrap some lint free cloth (PecPads) around, add some cleaning fluid (Eclipse Fluid) and wipe across your sensor to remove the dust. The difference between this and the blower is that the SensorSwipe actually removes dust rather than just pushing it around. You change the cloth each time you wipe it across the sensor.
Take the time to read this article. I believe it's also the place you buy the SensorSwipes from, but I can't remember for sure. Got mine over 18 months ago. It was shipped from America.
You can buy the Eclipse cleaning fluid and Pec Pads in the UK, although I can't say where from because it's a competitor.
You have to be careful, and sensor cleaning isn't for everyone, but personally I've found this to be an extremely easy and effective method for cleaning my sensor. Once you get over the "OMFG I might damage it" nerves, and read the instructions several times then it's simple. There are others on here who will confirm this too
Hope that helps anyway. Good luck!