I cannot recommend Johnston's (Johnstone's??) paints highly enough. I like rich colours. Used to whatever B&Q carries, I have always had to do a number of coats as one is never enough. Johnstone's paints are a considerably higher quality (one, or two coats max), and you also get much more personal service. With all of this, comes spectacular prices.
Whenever we go in, we grab a 10L bucket of primer and a 10L of white finishing paint, with each for not much more than £20. The colours are a bit more than this (about £20-£25 for 5L), but we are always in buying so much that the seemingly gruff wee guy behind the counter has a bit of dialogue with himself about how much he can take off to help us out. You don't get that kind of stuff at B&Q.
It's branded as "trade supply" but they aren't bothered if a regular Joe off the street walks in. The only down side is that their main opening hours are M-F and only until 11 or 12 on Saturday.
Don't be intimidated as I was the first time you go in, the staff really are all lovely but just used to dealing with professionals. It is absolutely THE best place to buy paint. read more