Total acceleration is very rare in the UK. Maybe if it was more normal we would consider it.
I don't think that acceleration by one year is very rare in the UK, particularly in private schools. Quite a number of my year at Cambridge had been grade skipped and entered Cambridge at 17 instead of 18, and when doing admissions (in Maths) for Cambridge it also wasn't unusual to see kids who'd been grade skipped once, even coming from state schools. Being grade skipped more than once in a UK school, and entering University more than one year younger than usual, does seem to be much more unusual. (I was in this position and there was quite some discussion about deferring my entry, gap years etc with my Cambridge college.)
