Apologies for the late reply, I began travelling and I've been very busy.
My family moved away for reasons completely unrelated to the school. IIRC how the sixth form admittance worked, I would have been allowed to do it there had I stayed and gotten the GCSE grades I did at my next school (889 for the subjects I took at As.) However I don't think the environment would have been healthy at all at that level.
I'd say my latter school as the environment was much healthier especially once it got to exam times, but I think HBS was a nice place to go to (not necessarily better, it's pretty difficult to judge, but the gap would be smaller) in ks3 when the exams were less important due to the lack of bullying, even though it still had issues back then.
I was tutored and pressured to a very unhealthy extent, however I wasn't some complete tiger parent horror story, I was still allowed to have a decent amount of free time. And no I'd say it wasn't, there are plenty of schools that are better in many respects that can be easily achieved with more healthy amounts of tutoring. Even at HBS exceptionally bright students stand a small chance of getting in with healthier amounts of tutoring.
It can be both depending on the student, but I'd say in most cases the students were no longer professionally tutored and mostly handled their own studying with parent micromanagement guidance.
I don't know anyone from either of those schools, sorry.
And thank you!