Yeah, in my rural area Jehovah's Witnesses occasionally show up at the door. Mostly handing out printed leaflets. One time someone who looked very meek and shy gave me a painstakingly handwritten letter in blue biro that must have taken them ages. I did read it after politely saying thanks and goodbye, and it was thoroughly unhinged and extreme oceans-will-boil-with-blood doomsday Revelations fanfic.
Cities get a lot more interesting. Walking round That London or Bristol, for example, you may well be accosted by anything from charity muggers to scientologists to people with more individually idiosyncratic convictions. I just solve it by never ever making eye contact and pretending to be deaf tbh, because I find the process of getting out of the conversation once they've engaged to be deeply embarrassing.
My French relatives have some sort of ground source heat pump, having designed everything in their home to work on that basis, and it is everything you describe in terms of size - the pump unit is huge and impressively loud. It worked very well, when it worked. Unfortunately, the underground bit is also broken and the installers who broke it have refused to solve the problem. There is a fair amount of cowboy engineering going on in this domain, it turns out, a lack of reliable support for existing units/installs, and of course the usual attempts to extort money from people of a certain age. It makes me sick that they did everything right and were let down anyway. I'm not saying avoid this technology necessarily, but if you get a lemon and/or are unlucky and hire shysters there is practically no ceiling to the costs involved.