Racing - Commiserations for AP's feelings of gloom. What form is Wriggle's annoyingness taking? Has it abated by now?
Daisy - you were playing lacrosse until a few years ago? Wow!
As for the schools dilemma, let's cut to the chase. Are these state schools? How over-subscribed are they? I ask because, around here anyway, it doesn't seem too difficult to change independent schools mid-stream, but the most popular state schools have long waiting lists which mean that if one's original choice turns out to be a disaster it can take a long time to move. So I think you need to think about what your escape route would be. (Having moved MBB between schools I tend to think about this a lot and probably give it too much significance).
But, more than anything else, I think you need to base your decision on (first and foremost) what will suit DaisyBoy. The little boys around here who attend the prep school which sounds rather like your school B seem a bit, well, squashed. Not unhappy, just not giving free rein to their essential boy-ness. Which may or may not be a good thing.
As for age of staff. MBB's education has suffered in the past, I think, through having teachers who were very young and very inexperienced and just didn't have the skills of the trade, which you need if you are going to hack it in a London primary school. So I would be wary of any school which had a vast proportion of newly-qualified teachers (especially as that might tell you something about staff turnover). But younger staff can also be energetic and enthusiastic, so I wouldn't necessarily opt for a school with a middle-aged staff. I also wouldn't be too bothered about the headteacher leaving - a really good school won't be dependent on the personality of one individual (even an individual as elevated as the head teacher) and if it's a good school will attract another good person to be the new head.
So that probably hasn't helped much.
Who'd like a steaming mug of hot chocolate?