Just to add my halfpenny's worth...I went to Wycombe Abbey thirty years ago(ouch!). Times have changed and I expect the school has too, but this was my experience:
I was one of the top fifth of my year and did have a very good experience, academically-speaking. What happened in those days is that , fairly early on, the staff decided which girls were likely to get into Oxbridge and concentrated on those. This meant that the other 4/5ths had a (relatively) mediocre education.
I remember an A-level French class where the four of us who were going on to do Languages at Oxbridge basically "led" the class and all the translation exercises done in class were given to us. The result was that the other ten in the class didn't do that well at A-level (relatively -speaking) because they just hadn't had the attention.
And I met up with a friend recently, who has done fantastically well in her career, who was saying how the school gave up on her fairly early on, and even made her do 2 A-levels rather than the three or four we normally did then because they didn't want her to skew their statistics by-"shock-horror"-getting a C or worse in one of her exams.
I would say about 50% were happy boarding there(and would/are sending their children there); 50% pretty unhappy(and wouldn't), with a small percentage desperately unhappy (the second part obvious!) Anorexia was a real problem, but maybe is is at all all-girls' schools.
Anyway, just wanted to give you a realistic picture of what WA was really like, but whether any of this still applies to the school today, I've no idea.
Good luck with your choice.