How much to board & skim this wall?

JustAnotherSaver

Hopefully can come to some sort of agreement with the guys who did the work on our house so we can avoid going down the solicitor route, so i'll be needing a good idea of price for this job:

Basically to board the walls & then skim. The height is 2.4mtr & the length of the wall is 7.0mtr. It juts out at right angles for the chimney breast but that's it, other than that it's a straight wall with no fiddly bits. They only boarded one side of the chimney & the chimney itself, so perhaps 2mtr of it was just skimmed (not boarded) & a 1ft(ish) 2mtr(ish) strip in there was bonded & then skimmed.

Any more info required or photos then just ask.

What would be a typical price for this work?

Thanks.