I haven't read through all of this, but as a recent (2006) Cambridge Grad, I would definitely advise Oxbridge! Particularly if he like music and sports. I am a state school drop-out (didn't complete my GCSE's, was a complete horror at school and became a teenage single mum) you really can't get further from the presumed image of an Oxbridge student! But, my goodness did I enjoy myself! I made friends very easily, there are so many different types of people - this is what makes Oxbridge so fantastic: it is built on a furious thirst for knowledge, and if you have something to offer you will be welcomed with open arms - this diversity ensures that everything is constantly looked at with fresh eyes, fresh opinions, fresh interpretations. Everything is debated and it is an incredibly awe inspiring experience! what's more, there are so many societies that you can be anybody! Seriously, there are societies for cross-campus games, that last for weeks on end, societies for every imaginable sport, every type of music, every religion, there are socialist/conservative/labour/green/etc. It is possible to find a society (basically a club) for anything and everything. But, even better is the books! Oh the books - every book ever published, at your beckon call (I spent one term at a less 'prestigious' university, and I was constantly battling to find decent reading/research material, and to find anybody to discuss theories with - an emerging idea needs feeding - mass debates over the dinner table are perfect for this!) The other HUGE tick for Oxbridge, is that the greatest minds center upon the two colleges - this is where all the resources, are, and where is is cool to be a geeky nerd - so it obviously attracts people who have a huge thirst for knowledge. Ask your son whether he would turn down the opportunity to share lectures/dinner/halls/socialise with the current/next Isaac Newton or ( _ enter well known scientist - I'm not up to speed with the sciences) Could he imagine the mind blowing discussions he could have, indeed, could he imagine how far this would stretch his imagination - he could be the next Isaac Newton, by the chance of pondering the inkling of an idea with somebody in the kitchen, or battling a theory out with his supervisor or something striking him in a lecture by Stephen Hawkins (or other present day genius) and it growing from there, into an amazing break through!?
Honestly, anybody who is serious about growing to their full potential, would be wasting a huge opportunity by not even applying!
I got on wonderfully well, despite my background (poor, state school drop-out), and learnt not only how to behave like an adult, but also to accept everybody as people - whether they appear rich/poor/snobby/shy... Of course there are cliques, but not as your son will understand them to be from school - they are not as well defined the dining halls/lecture halls/residence halls are a hotchpotch of all types and the most unlikely of people (seemingly) are great friends - people will value him for his intelligence.