The solution to this problem first we removed floor coverings and radiators we also removed curtains fitted our dust sheets and PVC to doors to stop the dust moving into other rooms. So then we had to drop the high ground levels to be able to get the new damp proof course in 150mm off the floor level.
External walls remove the wet plaster install new damp proof course fit plaster base tanking membrane there after fit new plaster boards ready to skim over with plaster finish once dry fit back the timber skirting boards and radiators.