Just to share a discovery I've made: I cam across some acrylic paints in a store in Glasgow. They are called MP (abbreviation for Miniature Paints - original I know) and come from a company called Gamecraft. I bought a couple of pots to try out not expecting much as they were so cheap. However, I was very pleasantly surprised when I tried them out. The paint covers very well (much better than Citadel) but you get almost twice as much in a bottle for half the price of citadel. They also fit in my paint drawer!
The colour range is really good and is complementary rather than duplicating the Citadel range. (though black is black and, if anything, the MP white is whiter than Citadel's!). Apparently the inks aren't as good so don't buy them.
Unfortunately, I haven't found a web site for them (though there seems to be distributors in quite a few country) but if you come across them in your local shop give them a go!