I went to the girls school about 100 years ago (alright, I left 12 years ago), so I can't really comment on its current ethos/results etc, although the grounds always made for a lovely atmosphere, especially in summer. Just seen that 5 girls got into Oxbridge this year, which is about the same as when I was there, so academically I think standards have stayed as high.
Are you thinking day or boarding? In my day (and I can't believe it's changed much) the termly boarders were a very tight knit group, often with the more local day girls, but those of us coming in daily from further afield (and quite a few come quite a long way) or the weekly boarders who went home at weekends tended to miss out a bit. If your DC can do some after-school activities that would help (we were a one-car family when I started, so no chance for me!).
I went at 7+ to the girls for a couple of years, my family are still in the area and know quite a lot of people using the schools. Habs (Boys and girls) are stronger academically than the local private competition, such as Hereford Cathedral and Rougemont. Still lots of kids commuting from Abergavenny, Ross etc.