scrappy would second MUA in Superdrug - especially their chubby lipsticks.
Aldi have a very limited but reasonably priced range of make up - the eyeliners in particular are very soft, have a smudger on one end and come with a sharpener.
Poundland is another place to look - they frequently have stuff from a wide range of makeup brands - I've had L'Oréal, Rimmel, Calvin Klein, Essie, Sally Hansen, Nails Inc, Maybelline and Burts Bees and more, and seen them all crop up on a regular basis. So no good if you need something particular on a given day. But, if you're able to pop in on a regular basis you should get a decent collection of bets before Christmas. It's usually best for nail varnishes and treatments (including some fun colours to experiment with!), eye shadows and blushers, and the burts bees/maybelline tinted lip balms which are nice.
The online poundstores can also reap rewards as can places like b&m and home bargains, but not quite as cheaply.