Definitely not posh. It was originally very much a West Country accent so quite rural, and then I lived in London for over 20 years and it faded a bit. It’s not posh, not particularly London, but not as broad as the accent I had when I was growing up. It’s not dead common, but also definitely not upper class.
I think Heather has potentially not had much contact (apart from her interviews with people) from different countries and probably still associates say a British accent with the archetypal baddie in a film or maybe even the cliche of a posh person from say Downton Abbey.
I was renting a car in Albequeque (is that the right spelling its after 1am!) and the ladies behind the desk were aghast that I had an English accent, obviously not many people rent from Dollar there who are from the UK. They kept asking me to say things and I was grumpy and tired and still had 125 odd miles to go to get to my destination.
Interesting. Definitely not RP and I was a bit taken aback how Heather seemed intimidated. It was weird. I find it amazing how many accents can exist in what is a relatively small area and I imagine to some degree there is blending or changing as economics, migrants, and class-structure changes. One notes how the BBC seems to be hell-bent on using regional, and even foreign, accents as opposed to before using "BBC English." I also enjoy how some people can "turn them off" or "resort back" depending on area. I think this mainly is more educated people? But Idk. Also learn to switch and also study how to "get over" an accent? You can be in meetings with Scots, for example but then go down to a factory line with them and not understand a word of them talking Glaswegian with the workers. Or how Pakistani/Indians can put on the "Indian accent" or talk normal, or even revert- still using English- to the heavily accented English when talking with their parents etc.