if you basically want to go to cambridge now, you must basically get 99% or 100% UMS average across all your AS subjects....otherwise its not looking great...
apply to places like keele, lancaster, st georges, hyms (this places to me dont have the stigma of having an academically rigorous admission process)...when and if you get 4As at AS....(no other bmat university, because thats just risking it)....