Crest whitestrips work. I bought the premium ones off amazon for about £20. I havent used them all (they would make my teeth hurt if I used them everyday) but already my teeth are bright white. Definitely recommend them
They have hydrogen peroxide in them which is how the teeth change colour, it is not damaging to teeth according to my dentist!
I had a look into this sort of business once, all I can tell you is to stay away from a lot of the stuff from the supermarkets as apparently a lot of them wear away your teeth.
If you imagine using a scourer on the inside of a mug... and the next time you drink tea from it you can see where you have scratched it with the scourer... well that is sort of what they do to your teeth. Never heard of crest white strips though, could give that a try.
If your really bothered by it you can get laser whitening from the dentist, I think its about £150 at a guess. Or do what one of my housemates does and claims depression, so gets lipo and botox etc. on the NHS the loser.