I don't know what Jon at RCS is stocking but I'd say he should be your first port of call for anything you need.
Aside him I'd highly recommend
www.everythingairbrush.com, who do chinese copies of the iwata's for about a quarter of the price. There is a difference and if money is no object I'd go for the Iwata, but getting yourself going I'd go for one of them. They also do compressors too but you need one that's going to keep up with the high pressure you need constantly. And as UPD says above machine mart are super cheap, you will have noise issues with their ones though. I think they do a quiet range though ?
To airbrush this sort of stuff I'd say a 0.3 to 0.5 nozzle is best, the smaller ones don't like our thick paint so you'll struggle to get it through them without thinning it down loads.