By the time my dc were in Yr 13 we (DH and I) called both head teachers Jane and Andrew and they used our first names as did our DC's most senior teachers paradoxically. We are now friends with DS's Housemaster and he and his wife come to parties at our house (when not in lockdown). DS is now 26 and would never dream of calling him anything but Mr Carter.
DS's school was very formal for the boys all the way through 6th form; at DD's however the girls called some teachers by their first name. Not sure if that was a trend as dd is 3 years younger.
Both schools with clear boundaries and high academic standards and expectations for behaviour.
I am happy for my first name to be used in almost every environment: bank, solicitor, accountant, dentist, etc, because in those environments the other parties are happy with their first names being used, interestingly I prefer Mrs Hellebores when dealing with estate agents but I think that's a "smarm" issue.
I do not accept my first name being used in clinical settings. My GPs introduce themselves as Dr Blogs and that's how practice staff refer to them. Therefore neither they nor their staff may use my first name and it is an equality issue. Personally if any Dr in any setting expects to be referred to by title, then everyone else in that setting, including admin staff and nurses, should be afforded the same level of courtesy including by Mr Pompous-Arse consultant surgeon.
I can see that government ministers may expect to be address by title and can acknowledge they are above the hierarchy of an hospital consultant but having said that, all the Ministers I know generally use their first names, and I can vouch that John Major, David Cameron and Boris Johnson do. Having thought carefully of DishedUp telling me to get over myself, actually I think the boot is on the other foot.