Obviously peer group is very important, and I think the general culture the child is working in is crucial. 100% of the peer group going to RG Universities wouldn't bother me at all though, in fact if anything, it might turn me off a litte, as it smacks of following the herd.... often the really interesting kids are the ones who have a different persepctive, or a great entrepreneurial idea etc. But yes, definitely a good proportion of kids who are goint on to higher education at good Universities.
I think there are so many variables that it's too simplistic to think that if you fork out lots of money, then your kids will turn out fine and happy and successful. For a start, getting into a good University isn't the end is it... in many ways it's just a beginning....I bet we've all known young people who went to expensive schools, jumped through the required hoops, got into a good University but then found themselves unhappy, or unable to cope with the level of independent thinking required, or just not 'fitting the course'. I certainly came across a few types like that. And then of course there's all the other areas of life that are hugely important in determining well being... being able to relate to other people well, having self belief (and I mean, genuine self belief, not a glossy veneer of confidence that is bred into the worst private school types), having the insight to pick a good partner for marriage and parenting.... all these things contribute hugely as well as academic achievement.
I agree that music, orchestras and other interests are very important too, and I think if you value these things as a parent, then you have a duty to instil these values in your offspring.
Sitting in lovely school grounds doesn't cut any ice with me I'm afraid... my own garden is lovely, or I'd use my National Trust card to sit in a stately home garden if I feel the urge... can't be doing with paying school fees for that. And the thought of joining a school choir as a parent would be the kiss of death...
Overall, of course it's up to individual parents to look at what is on offer in their locality, and I'm sure if I lived in some parts of London I wouldn't consider I had any choice but to pay, which is very unfair and bad luck on those in that situation.
I do think the value for money is an interesting thing though. If you don't qualify for scholarships or discounts, you're looking at around £1000 per month per child at private school (and that's before extras such as uniform, trips and that dubious textbook charge for using the school text books!!) which for many parents is a lot out of taxed income, and many of them want to be sure they are getting a good return