Les choses qui fachent

As the works are nearing the end, I am on a high to see the end of this project. But there are things a little less nice to deal with: ie the invoice from the main contractor Mr M.
Mr M is a nice man, very obliging but now that he gave his final bill, I am not very happy with a number of items and the end cost.
Dispute about final cost is often a problem with buildings works and I hoped to avoid it this time but I did not, once again.