Another thing to consider is how he likes to learn. My DD1 is currently studying medicine and while she also had the grades for Oxbridge, she wasn't keen on the lecture based learning style which is prevalent at the colleges there. She opted for a University that focuses on PBL (problem based learning) ..there is a lot of self study for case units, but also lots of group work/tutorials and it's very much hands on (terrifyingly so IMO ). This suits my daughter's learning style very well, but obviously if your son prefers lecture style learning, Oxbridge is ideal.
In all honesty there is no superior University for medicine due to the nature and demands of the course.. those who manage the five years are doctors and many fall alone the wayside as most Med schools 'cull' the lowest performing students each year even if they pass the exams.
I'd encourage your son to simply go and look at what is on offer at different places.. my DD1 was convinced she would like one best..then after visiting them all, changed her mind, falling in love with the one she is at now.
Wherever he applies he won't be wasting a choice.. Medicine is incredibly competitive and difficult to get into , but he has fantastic grades and if he can get a reasonable amount of work experience and can provide a personal statement that demonstrates what he has learned from his WE and show a real passion.. he will get interviews and offers! Incidentally WE doesn't have to be just shadowing doctors or suchlike.. pushing trolleys round old folks homes, leading boy scouts.. anything that shows people skills and a bit of sense, helps!
Oh and the balls and whatnot tend to be expensive wherever they go... but it IS possible to do a bit of p/t work..DD1 also works in the holidays.
Good luck to your son:) DD1 knew she wanted to be a doctor when she was 4 years old and I still can't believe she is really there, really doing it. She is just going into her 3rd year..clinical..now and is extremely excited as she starts on Monday! Oh and she came from a bog standard comp.....one one of her interviews she was the only state educated person in the group, but they really do look for ability not the name of the school:)