Classical Music Downloads in the UK
You can listen to 60-second sample before you decide to purchase.
The music is catalogued by Composer, Artist, Genre or Labels. I found it interesting their banner ad is from Naxos... There is also a blog which has a few articles worth a glance as well.
It seems like this site was a good idea and yet is having teething problems.
Tom Service, at the Guardian, is a Mac user and not have much joy with his downloads (as per his article). However, he speaks highly of it, so there's hope.