slhilly: you keep changing your stance, bit by bit.
You began with: "Why can't all-staff training etc take place before or after term-time, during some of the 13 weeks of holiday teachers get?" People pointed out that this does in fact already happen.
Then it was: "I see no practical reason why teachers couldn't stay on for an extra week in the summer and do all their training in one go then, once the children have left." People gave valid reasons why this wouldn't work professionally as we need opportunities for training throughout the year.
You then said: "If the Inset days were at the beginning or end of a term, so that term-time was one contiguous block, it would be no big deal." People pointed out that Inset days are, in the main, organised like that, unless term starts/ends on a day other than Mon/Fri. Schools used for polling stations have no choice but to close on (usually) a Thursday.
"Blocks are easier to manage than random days, for most people. Random midweek days are hardest of all to manage." For you maybe. But plenty of others complain about that and prefer them scattered.
"I've said it elsewhere here, but the key thing for me is that the training should not be during termtime to avoid this: Mon - school, Tue -school, Wed - no school due to Inset, Thu - school, Fri - school.
That is all." No it isn't. You said it should all be in one week in the summer. THIS is your main change of stance.