Max knows to his cost that dust gets onto your digital SLR sensor all to easily!
I have also been plagued by this problem frequently but thankfully I am now able to clean the sensor myself after being shown how to do it by Peter Brogden from
Just the specialist camera cleaning company
http://www.cameraclean.co.uk I bought one of their kits last autumn at a Royal Photographic Society digital day and have used it to great effect. I have now bought some fresh supplies whilst at Focus and Peter is also donating a pro kit as a prize in the DPS competitions.
They sell various things to remove sensor dust and I bought one of their introductory cleaning kits with sensor swabs and eclipse fluid. It is easy to do if you have reasonably steady hands and the results are great. You can download a pdf about how to use the swabs and fluid from
here or on the website above. The kits are £22.95 and contain enough stuff to clean your sensor 5 times, about £6 a go. The fluid and pec pads can also be used to clean your lens.