Two of the best sources - both recommended to me by excellent people - are TeNo in Cavendish Connect and the Zoppini kiosk at the V&A Waterfront.
Zoppini is from Italy and is a more aggressively priced option. Less jewellery and more funky accessories, this line is a must have for the trendy boys. I don't think you can get better these days - and definitely ask for a discount. They will do their best to help you out.
TeNo is a German brand that is favoured by Paris Hilton and Eva Longoria. It is pricey but the craftsmanship is excellent and they currently have a 40% off promotion running. They also have some quite innovative pieces will with steel core so they will last a lifetime. The store is managed by Azeema who is very knowledgeable and helpful.
