With an estimated 27,000 stores in London, there is certainly no lack of choice for the visitor.
At the top end, there are more leading retail brands shops in London than anywhere else in the world. But that is only part of the appeal of shopping in London ,it also has a large range of independent shops which caters for a vast range of products.
Some areas are known for particular shops ,for example Savile Row for quality clothing. It is in the independent shops and Museum shops that you are likely to find quality London Souvenirs.