Thank you for all your advice which I have taken on board. We are at present not going ahead with the project after getting a quote twice what was originally quoted by the builder aka their uncle. It feels like wed be part paying theirs too. So back to original worries. We have asked they build no further than their boundary not astriding it which they have agreed to although the bit the juts in is still a sticky issue. We bought house with fence as it is and the jut runs from the side alley right to bottom of garden so a very established line. It's difficult to see on plans though as it starts mid alley. Yes I don't really want extension tbf and only considered doing it together so we didn't have to look at it. But I'm not prepared to pay a silly price for it. So where do I go from here is I guess what I'm asking. I don't want to fight with my neighbours as they are nice if a little selfish at times but I also don't want my land to be put a jeopardy or be intimidated by their builder. I feel this is going to be a fair few months of stress as they also won't give us plans (unwilling to do the) so we can't council their intensions