Your first step is to find your local paint shop and have a chat with them. If you don't know where it is, ask at a local accident repair garage who supplies their paint.
The two basic paint types are cellulose and 2-pack. 2-pack is the professional choice, but it's more expensive, is dangerous to use (you need a respirator) and ideally should be baked to get a hard finish.
Cellulose is a drying rather than hardening paint, so it's better suited to amateur spraying in your garage. It's cheaper too - you should be able to get a basic colour from £10 a litre, metalics and pearlescent are more and are more difficult to spray.
You'll also need an etch primer, high-build filler, and if you're using anything other than a basic colour, a clear laqcuer too, not to mention panel wipes, thinners, G3-G10 (T-Cut), wet & Dry paper etc.
You should be able to do your car from about £100, or if you could afford a little extra and are worried about getting a good finish yourself, you could do all the prep work up to the primer/filler stage then have a professional garage do the top coats for you.