Thanks for the reply.
My neighbour has not informed me or ask for permission to do what he has done under the Party Wall Act either through a letter or informal chat. I had confronted him about it but he was hostile about it.
I had contracted both the Enviromental Health and Building Control departments both couldn't help me. Enviromental Health said that because the noise was a result from the alteration of the walls, they had no laws which can bring the neighbouir into account.
Building Control came round to check both my property and next door, eventhough the guy next door was reluctant to let the inspector in, only after the threat of a warrant was he allowed in. The inspector found to my surprise that the chimney breast was still there although a fire place was put in, eventhough when I knocked on thier door a week earlier the fire place was absent. Whats more strange is the day prior to the inspection I can hear from next door a mad rush on a big DIY job, I could hear the hammering, drilling e.t.c. This went on for nearly 20 hours, the guy next door didn't even sleep. He worked from the morning and into the next morning, because he is used to working the late morning shifts. I am suspicious that he may have friends or relatives with the council who may have given him the heads up on the inspection.
I am really stuck now, can anyone please help?