Paul Whitehead
If the damp is close to the ground it may be rising damp, moisture could possibly be breaching the old damp course. If so you will need to speak to a damp-proofing company with a view to having the walls injected with a liquid DPC. If its penetrating damp please refer to my previous answer. It may well be worth getting a specialist to survey the property before approaching Renderers/Damp Proofers etc for prices, that way you can provide them with a copy of the report on which they can base their quotes. Good luck.
