a word of caution, Trafalgar Square if good fun, but can be quite scary on New Years Eve, just take the min amount of money req, i.e. beware of pickpockets and dont flash your mobile phone either. Just be aware that not everyone there is kosher.Leicester Square at night is also buzzing with activity and lots of people, we had some Russian friends who thought Leicester Square at nights was wonderful, another place not to miss is Convent Garden which is within walking distance of Trafalgar Square.