I agree with what FmF said, plus:
Rust-O-Leum do a chalk paint range that seems to be well reviewed, and is available in Homebase. Limited range of colours, though.
You don't need to sand, though I usually do a light sand and of course a clean. I have, however, used it to paint a kitchen table and chairs that were heavily varnished, with almost no sanding. It went on fine but a year on it is very chipped, grubby and worn - I can live with that because my table, bench and chairs cost me £20 total [bargain junkie preen] and also because they're country style so I've just mentally classified them as shabby chic. If you don't want the battered look, though, I wouldn't use chalk paint on stuff that will be bashed around.
I've also used it on low traffic furniture - side tables etc - and the effect has been really good.
It's really worth taking time to wax properly, and do at least three coats.
You can order Annie Sloan online. The accessories are very expensive - I bought one good quality brush, but I don't think that's vital. For waxing, I just use lint-free cloth.