Damp proofing mid terrace 1900s property

Hi, I am looking to buy a mid terrace property and have had a surveyor report completed. This identified rising damp in one of the downstairs rear rooms, on the two side walls, one of which is a party wall with nextdoor and the other which is open onto a courtyard. There are invoices dating back to 1967 where the floors in all downstairs rooms were dug out and re laid with damp proof membrane, but I assume this wouldn't have included any work to damp proof the walls themselves. Also the living room walls were treated for damp in 1967 too although these have been fitted with a dado rail and what looks like panelling that sits about 2 inches away from the original wall to the dado rail height. This was done at the same time as the flooring and damp proofing, but no explanation as to why. So what would be the likely amount of work involved in treating any damp in both of these rooms and estimated costs and is this something that I should be especially wary of or something that is easily fixed?