Warwick and imperial are amazing unis for maths, great choice. With a good TMUA score and predicted grades, you should stand a really good chance of getting in. Obviously oxbridge is the best but it is up to you if you want to apply there, I'm not gonna tell you what to do bc obviously its a big commitment. Other good options are edinburgh and st andrews, but they are rather selective, especially if you are from England. Safe(er) choices would be UCL, durham, KCL, Loughborough and manchester.