When you say 'London' do you mean London University (which doesn't exist as a single institution) or did you mean Queen Mary University of London?
If it's out of QMUL and Warwick - they are both very good universities. Queen Mary is excellent for Law and has recently joined the RG. Warwick is a fantastic Russel Group university, full stop.
Warwick generally is a far better university and it requires AAA whereas Queen Mary requires A*AA. If I was you, I'd go for Warwick. Its employability rates are fab too.