Sensible advice first mate. If you get on very well with your neighbours it's possible to go down the DIY route and sort out the Party Wall Notice and Award yourself in conjunction with your neighbours, thus saving the costs of a surveyor. But even then, neighbours can subsequently fall out and disagree, people quite often do when property and money is involved. That's why I always think it's best to appoint an experienced third party. And when you have a neighbour that's clearly behaving antagonistically, as in this case, there is no option other than to appoint an experienced third party. Building Control approval is a separate process from the Party Wall process. A PW Award needs to be in place before any works commence, which usually takes a couple of months. With works of this simplistic nature it's common for a builder to issue a Building Notice to the Council 48 hours before works commence, This informs the Council of the imminent works, and should include the Structural Engineer's drawings and calculations. A Building Control officer will then visit site to check the work has been carried out correctly and issue the appropriate approval documentation...