London would be the largest city in Europe and has some of the best attractions and activities. For any city break I would definitely propose London generally for everything it can offer from great heritage and architecture right through to some fantastic theater and nightlife.
Depending on the season which you visit there are also some great sporting attractions to go and see for example Wimbledon for some excellent tennis along with the world famous Oval and Lords cricket grounds for getting a game of cricket. Had you arrived a few months back you would have been in a position to witness the fantastic Olympic Games that was put on from the UK in the east of London.
Should you really want to go around and see several things outside London then I would advise renting a car which happens to be reasonably inexpensive, but if you plan to go to the rather busy west end of London for a spot of shopping then I would personally definitely recommend leaving behind the vehicle at the hotel. Despite the brand new congestion charge in the capital has been introduced, it is still a nightmare to get around.
Try to keep up to date on travelling in the capital and surrounding places by going to the BBC news site or seeing the news channel. This may alert you to any large problems on both highway and railway networks which can help save some time when planning your trips.
I would also suggest to absolutely have a look at the London night life while you’re in town and for this you can pick up any publication or search on the internet for the latest activities and performances in and around London.