I still don't understand the fascination with shopping in-store, so much hassle, especially in London. I've given up - just shop online now, my current favourite webstore is http://www.not-addicted.co.uk/product-category/brands/ma-strum/
You get some decent clobber without having to leave the house :D
However, if I were to pick my favourite shop in London - Weekend Offender - D'arblay Street - Top quality. Clothes are ace and the staff are top lads.