Unfortunately I can't recommend anyone, but I had experience of this 21 years ago when the neighbours I adjoin excavated a basement.The people doing the work have to pay for your party wall surveyor, you can choose whom you like. The surveyor's loyalty is not to you the client, but to the wall. Sounds odd, but apparently that's the way it is. Have you tried Which Trusted Traders?
Elizabeth Balsom ● 1410d