Since no current or recent parents have turned up, I'll give you my thoughts.
It's a good school for the right child. It suits girls who are socially competent, resilient and happy to conform, both to the demands of the school and to fit in with their peer group. It can be quite cliquey - bear in mind many of the girls come en bloc from the feeder primaries, and friendship issues from junior school can be carried straight over and even escalate.
IMO (I'm sure others would disagree) it is less likely to work for a girl who is super-bright and highly verbal, or someone who is quirky or unconventional in some way, or who has social or friendship issues.
I know lots of girls, ranging from current students to girls now in their 20s, who had a great time there, but also a number who have been really unhappy, mainly falling into the categories above. Horses for courses.
If you're local to the school, do look at Parli which (IMO) has much better pastoral care and a less conformist vibe. If you're Catholic and further away, do also look at St Michael's in Finchley.