Looking for someone to skim coat ceiling

highdef

Hi, I bought a shell of a house about 5 years ago and like all things in life, it is still a work in progress. Anyway, one of the rooms is going to be a large living room/cinema when complete. The room was originally a small cottage. I had to get it dry lined and insulated as it was just bare stone initially. The ceiling did have plasterboards but not in the best of nick and no skim coat. When getting other things done in the house, I asked a builder if he could do a job on the ceiling but he said he couldn't because the plasterboard had gone off. Can this happen and would it mean it would not be possible to skim coat it? I'm thinking he just fancy doing the job but I could be wrong!
I have a few photos attached that should give an idea of what I need to get done.

Secondly, if anyone can do it or knows someone who can do it, please feel free to PM me any contacts as I really want to get started on this room.....it was being used as a junk room but since I got a shed, I have started moving stuff out of it.

fussyonion

The builder was right. Those marks will come through the skimming.
What you can do is, get a hammer, puncture where the joists are and re-slab it and then skim it.
If you're anyway handy you can do it yourself.