A few options you could try.
At the bottom end theres the Sony MDR-EX71, which are not technically noise cancelling, but offer a high level of attenuation. The sound quality is rather poor on them IMO though, and as such, its probably worth paying a bit more for....
Sennheiser PXC-250, which is a sits on the ear type design with a headband. It has active noise cancelling capabilities, but from what I've read, is not entirely effective, and also has a result of making them rather difficult to drive for some portables. If you can get an audition it might be worth trying, an audition would be highly recommended IMO since they arent cheap.
Other than that, you are pretty much looking at the Shure E2C (check ebay) or the Etymotic ER6, either of which should cost less than £100, and are like the EX71 in that they are canal phones and offer a high level of attenuation rather than active noise cancelling.
Or theres them Bose noise cancelling jobs, but I dont know how much they cost, or whether they are any good.