Obviously Oxford/Cambridge are the most prestigious, however the maths and stats course at Oxford happens to be the MOST competitive course that Oxford offers with a 4.9% acceptance rate. Cambridge also doesn't offer a maths and stats course but you can specialise in your 3rd year into stats. Outside of these two, Warwick probably shines brightest with an excellent maths and stats department. You should stand a good chance of getting into Warwick if you're predicted an A* in maths and further maths and do well (6.5ish) on the TMUA. If I were you, I would focus on getting high predicted grades and preparing for university entrance exams such as the MAT if you intend to apply to oxford and the TMUA for imperial and Warwick. Also, a good personal statement is required, but not an excellent one. Its always better to spend time DOING maths eg. solving problems than doing stuff for a personal statement.