I have a place at UCL. Your application looks good, but every year they reject great students so it's not guaranteed.
Grades are important to get their attention, but the contents of your PS are the clincher.
They care a LOT about work experience and volunteering and the like. By the time interview comes around, they will have already decided they like you academically, so you can wow them with the extras. Best of luck and don't become a UCAS whore (doing all sorts of nonsense just to put in in you PS/Ucas Form)
Also not too much BS in your PS :P
ETA: Ace your BMAT, because they use it prominently in the process of shortlisting for interview