We are 2 adults and 3 teens (ages 16 to 20) traveling to London for the first time for 7 nights over Christmas. We would like to rent an apartment type accomadation so we can have kitchen facilities but don't know what area would be best. We like to walk to most must see places but are fine with the tube to some. Most important would be safe and central to restaurants and pubs for evening since I am sure the teens will want to wander without us. Budget is around 400GBP per night. Recommendations please.