We live in a half house and I think it is correct that the dividing wall is not a proper party wall but more like the wall between one room and another. Is quite an odd set up - there are some floorboards that go right underneath the wall between us and next door and when our neighbour stands on a particularly squeaky one on their landing, it creaks on our side of the wall which is quite disconcerting in the middle of the night... When we had our kitchen fitted, our builder managed to drill right through into next door's kitchen when fitting a socket which also suggests the wall isn't very thick. Not only do we get more noise from the neighbours in the other half of our house than from the other side, we also get smells. In particular, our next door neighbours are heavy smokers and we can smell cigarette smoke in our house quite frequently.