Hey! Firstly, Exeter offers are absolutely not as high as Cambridge's, and if you've made it as far as to get an offer from Cambridge then you should definitely give Exeter a go through clearing (extra is closed, i think?)
ALSO I have heard of a girl who didn't get the grades for Cambridge, went to Kings instead and went through the transfer process (although you should know that she was absolutely crazy about cambridge, did all the research on the transfer and was met with excellent staff at kings who was more than willing to help her). She was attending cambridge by the end of the semester!
So that's another option. Have you visited any other unis? Personally my first is exeter and my insurance is loughborough, based on location, study abroad options, ratings/league tables and curriculum, as i never had the chance to visit them beforehand (failed art last year and had only visited unis for graphic design... had to start over). so if you do deep research into some other good places you may end up liking them as well (though never as much - i wanted cambridge as well, i can understand that. it does fade with time, though)