The Amazon UK/US sites have such a comprehensive range at competitive prices, that I feel there is no reason to look elsewhere. I once ordered from Presto Classical UK, because it is a dedicated site for western classical. But I never received the box set I had ordered. Although the money was promptly refunded after a 45 day wait for the parcel to arrive.
I have ordered and received more than 20 parcels from Amazon UK since Feb 2011. I got most of them, 10-12 days after the date of dispatch. A couple of parcels took longer to arrive. Only one parcel got lost, and after a 45 day wait, they have sent me a fresh parcel of the same.