i have a patch of damp about five foot up my wall, about the size of a dinner plate. its not anywhere else so could i paint some damp seal paint on anmd then put emulsion overthe top. is this going to work? ta

have you found the cause ? leaky pipe maybe buried in the plaster or maybe poor pointing if its an outside wall with no cavity.... the damp seal paint is of limited use - it may work for a few months but its no long term fix. If you do go down the route of using the damp paint cover an area far bigger that the current stain and use at least three coats

If you put damp proof paint on the water will only find its way out in an area that hasnt been sealed.
Follow scotty's advice about getting to the root of the problem.

thanks guys, not sure what the cause is, its on my party wall in a couple of places but its well off the ground. it will have to involve stripping plaster ooff whole walls so i would lobve the damp seal to work!

Not necessarily if you find the source of the damp ie a leaking pipe, all you'll need to do is let it dry out, stain block and re-paint.
Damp seal will not work!