Prendas.

I agree - I've only purchased a couple of things (Very nice merkalon armwarmers and overshoes) but the site comes across as being run by a decent organisation and service is excellent.
ps not sure you can get *everything* there though - they don't actually sell bikes..

Dunno how to compare online bike stores but I got a top deal from Winstanleys on a BMX race bike for my son.