I've got one of these, http://www.halfords.com/motoring/car-cleaning/interior-cleaning-vacuums/black-decker-dustbuster-12-volt-car-vacuum it sucks. Not in a good way
Blows dust out the side, the attachments fall off, it's only virtue is being 12v so I don't have to faff with extensions. Buy cheap, buy gash. I may well be treating myself to some sort of Dyson for Christmas.