I recommend getting a set of Vallejo paints. The "Game Color" range matches very closely to GW's Citadel range.

Vallejo paint is just as high quality for a fraction of the price of GW's. The eyedropper paint containers are also a great feature over the GW pots, and have a lot more paint per container.

We order all our paints from the GW online webstore.

There are several other alternative ranges, Vallejo, Army Painter, Scale 75, etc. All have there pros and cons for varying prices. We use the Citadel paint range, which has a wide and comprehensive selection, and we have always been satisfied. We think though that for the best results you could choose the best from all ranges. Some people complain about Citadel pots, but in our experience, if you keep the bottles shut tight and maybe drop some ball bearings in to help mixing, they last for years. And the paint is naturally rather thick inside, so you have to water it down, which means the bottles give a lot more paint than you'd expect.

Hope that helps,