cost of repairing damp on the ceiling

just got house we have a bid on surveyed and the chap said that structurally the house was sound, but there is some damp on the ceiling of the kitchen where the bath above had not been sealed properly. We'll have to get this fixed ourselevs when we finally get the key (fingers crossed), but we are wondering how much would something like this cost so we can budgeet for it. Is it a big job or just a few minutes work?
Cheers

I presume that you will first have the bath sealed correctly. If the damp patch is very bad and has broken or "bubbled" the ceiling you may have to replace the slabs on the ceiling. I'm pretty handy at the diy stuff and I wouldn't attempt to do this myself. If the patch has dried out it can be painted out. My Dad told me years ago to paint the area with undercoating and then repaint the whole ceiling with emulsion. If you don't mask the DRIED damp patch with the undercoat, the patch will keep coming through the emulsion and be unsightly.

I've seen undercoat used in the past to mask the dried out damp patch on the ceiling. The other thing that works very well is aluminium pain on the damaged area. We got this tip from a tradesman and it gives great results.

All above are correct- aluminium paint will block out pretty much any stain. It's often used to help paint over creosote and the like.

Yeah , concealed a damp patch stain before selling my house by putting 2 layers of undercoat on the stain and then 2 layers of emulsion over that ,it worked perfectly.