It's simple, Dreamer. Give up on Cambridge - you won't be going there. Focus like a lazer on finding 4 med schools that will consider, hopefully favour, your application. Do this by studying their prospectuses and reading the threads here on each individual med school until you understand exacty what they are looking for, not just their minimum requirements (that's a whole other story). There is no short cut here, you need to do it and stop getting everyone else to do your homework for you..Then make absolutely sure you jump highest through every hoop they want .... AS grades, high UKCAT, specific emphasis in PS, whatever.
You are already at a significant disdvantage - don't make it worse by trying to correct those mistakes while ignoring the uphill task ahead. It can be done, but you need to get into gear today.