Thanks for all the replies, really interesting.
My DS is already pretty mature this way (I think actually, having two GCSEs last year, one of which he tried to wing until after mocks, really drove the message home. He seemed in a way to grow up in parallel to your lot. And I am slightly furious that the school he and DD attend, supposedly because of the "new GCSEs", are taking that opportunity away from DD, Year 8, who I think has maturity issues anyway as a summer baby. I really think an early GCSE, even if she didn't do so well, would help her immensely for the main set).
DS is working exceptionally hard, and takes full responsibility these days, all I do is feed him and buy new protractors and such (and be the butt of periodic meltdowns, as the stresses are immense).
But I guess I am worried about mental health and stability, getting over this GCSE hump only to hit more pressures.
I confess, for what its worth, I really enjoy lurking here because of the window it gives me into next year (just as I enjoyed mostly lurking last year). I would miss you all if you went to cluster, although that is not a reason not to move.