I haven't done rather, ill be doing starting on the 19th September this year.
I'll be doing a maths masters at Bristol.
I would advise you not to totally set your heart on a university yet. I know some people who got really disappointed. Besides which, have you even visited imperial? I thought I'd want to go to St Andrews before i visited it but i much preferred Bristol when i visited them so I turned down what is often thought to be a "better" university because at the end of the day Nottingham, Manchester, Durham, Bristol, Bath, St Andrews etc etc are all good universities and you wont get a bad degree from any of them.
Imperial probably is a bit of a cut above these but don't go somewhere based on others' expectations. You should pick somewhere you like. Personally, I hated imperial (but i am bias against London).