I live in a red brick semi detached property. My neighbour has a single storey extension to the rear. I want to do the same. When I had plans drawn up it became apparent that the neighbours have crossed the party wall line by approx a brick and a half with their extension. Ok, well I'm a reasonable person, it was there years previous to me living here. Bit annoying but....anyway spoke to neighbour and asked if I could tie our brickwork in with his when we do the extension. Also having a gap between properties is not good due to damp etc so he was fine. Since then I have given him plans and told him I was keen to get started asap and informed him my builder was free to do job asap. I said I'd serve PWN, he'd never heard of one before, although I didn't give him two months notice, reason being he'd been ok and I thought he'd just sign it Tbh. It was at this point he started to get funny, saying he wasn't happy with us digging near to his foundations. He wants another skin of breeze blocks against party wall which I'm not prepared to do because I'm losing even more space, the builder said he would put some kingspan against wall for noise reduction as he was wittering about that too. He seemed ok(ish) at that. Said he'd sign PWN after he got back from holiday. He said we could start the build but not build against his wall until he comes back, which although annoying we did as asked. Anyway building control came, apparently we cannot tie our bricks in with his extension as his isn't even straight. So we will be building next to it. Anyway he's back from holiday and we have knocked on his door etc to ask how we move forward but he seems to be avoiding us. What will happen if we just go ahead and build our extension. It's so frustrating especially as his wall is on our property. It's a cheek and a joke now, the guys extension isn't the best, building control guy said it's not even straight, leans forward at the top. His bricks don't even match his house, Can we be made to take it down what will happen if I go ahead and build??