Thanks guys for your excellent advice. BTW, any good sites for buying paint and other stuff associated with spraying - filters, viscosity cup, solvents.....
I use an old Clarke compressor which doesn't even have, or need, a tank. It's compatible with a cheap Clarke spray gun which is designed for low powered compressors like mine. The results are quite good and certainly better than using spray guns. A single litre of car paint is almost enough to respray a whole car, once it's diluted with lots of thinner to the correct viscosity.
Try http://www.morelli.co.uk/, not a branch particularly close, but I think they will send items out. The Bristol branch are always great to deal with.