A colleague and his family went to London and Paris for a holiday last summer. The spent more time in London because as he put it, there were lots more to see and do, plus he managed to get good rates at a hotel in London. They visited quite a number of art galleries and museums, entertainment spots, parks and of course, they shopped.
Staying at one of the Knighsbridge hotels,Harrods was one place they went to. They spent almost an entire day at Harrods. Each of them came away happy having bought something for him/herself. Other places they shopped at included Marks and Spencer, Miss Selfridge and the Kensington Market where they picked out nice accessories.
If one is in London, there is no shortage of accommodations, some are even cheaper than hotels. For instance, hotels at Kensington area can be as low as GBP14.