RICS surveyor indicated high damp readings in exterior facing walls

This age of property will have been built using lime mortar, if it has been re-pointed using a cement based material or replastered using modern materials this will trap water in your walls. Modern and older materials do not really work well together, older buildings require lime mortar, plaster to allow them to breathe. Chemical injection damp proof courses do not work in this type of property, would be as well digging a large hole and throwing in some wonga as it would achieve the same result. You need someone who is used to dealing with older properties and how the different materials work together. All these materials are still available from specialist suppliers, a bit more expensive and harder to use than modern building materials. Finding someone to be able to use them might be a tad harder to find. There is no cement in lime mortar, anyone who tells you any different run a mile from. Should you require any other information, just ask. Good luck Alex