Again it depends on the type of damp you have, but we think, as do our neighbours who did them same, that our damp problem was helped by installing guttering. We installed the metal continuous type, with plastic downpipes. It costs us, I think, just under £200.
We also used the 'waterproofing' liquid described above by Trainer, on exposed wall that is made up of stone and mortar ccladding, and again that helped. A few quid for the gear, and a couplke of hours painting it on.