I have children who are currently at this school and who have left. Shootingatpigeons information is entirely accurate in my experience and matches my own exactly. There is some misinformation on this thread though.
There are some traditional boarding families but the changing economic environment means that the mix is not predominantly 'jolly hockey sticks' many families are first time buyers and a significant number are British expats whose fees are supported by employers or governments, or who earn high salaries overseas.
I believe that 20% are international students. For parents very concerned about that, it might be worth checking the make up of our most selective universities and places of work to see the mix of nationalities your children will be working with later in life.
Several of my daughters' best friends are of other nationalities. Efforts are made to keep houses similar in make up so choice of house is not important, unless your child doesn't like her housemates, but you won't know that until they get there anyway. Sometimes Girls of other nationalities like to spend together and in older years cook their own local food for example, but they are fully integrated. I think anyone who has expat experience will identify with the need sometimes to be with your own countrymen. These girls are usually intending to go to uk or us universities anyway and have remained firm friends with my older daughters after leaving school.
It is a larger school than most so although it is similar to Wycombe in terms of numbers of academic pupils, it has a lot more pupils and so is less selective at the bottom, hence the proportion of girls attending Oxbridge/Ivy league is smaller, even though the actual numbers may be similar.
All round development is excellent and the current head is especially keen on this. There is a vast selection of activities for the academically inclined and for those who have different talents - too many to take part in everything you might like. There are also activities at different levels so that you can enjoy an activity for fun even if you are not particularly good at it.