Good luck man, I had a similar ambition last year and it worked out. You've got a solid base to build on with those AS results and it sounds like you are doing a lot of work very early which is what you need really. I actually ended up with similar Maths UMS to you and took essentially the same further maths modules: I just took D1 instead of M3. M3 is probably more useful. My advice is to keep up the good work, just don't burn yourself out too early. Have fun as well as there is still several months to exams, work consistently like it seems you are as that will reduce stress at the end. Seriously though don't go too crazy with work in the beginning, you need to be steady and consistent. That's just something to be aware of, I'm sure you know what you're doing. Good luck!