The ones on this page are a good start
http://www.everythingairbrush.com/ac...AS_Series.html
And you can pick an airbrush up for about 30 quid, if you bought them together I'm sure they'd do you a deal !
http://www.everythingairbrush.com/ac...vity_Feed.html
If you want to practice get down to your local art shop and buy some water colour in tubes or ink in jars, both reasonably inexpensive. You can practice on thick paper or buy an airbrush pad ( super dense thick white paper, you can cut film on it and scratch out highlights ), or you could try some of these inks,
http://www.everythingairbrush.com/ac...ro_Colors.html
Get your primary and secondary colours and also maybe a black and a white although doing stuff on board / paper you really want the white of the board to show through as it's a brighter white than if you try and paint it. Personal preference though.
You can learn to paint with the airbrush and get the feel of it that way. When you get a bit more cash if you want to work on canvas Liquitex Acyrilcs in the jar / bottle, not the tube ones is really finely ground, goes through the airbrush lovely. Very good stuff.
Then once you're sorted move onto the body shells.