Dampness can originate from a variety of sources. Just because you have dampness at low level it does not necessarily indicate a rising dampness issue.
In the first instance you should take a look externally to see if there is any obvious water source such as: High external ground levels, Earth bridging the damp proof course, ensure the gutters and rainwater pipes are not discharging onto the brickwork.
Internally check any adjacent plumbing or wastes. If there is mould present then it may be a condensation issue.
If no clear sources of dampness are found then just post your job on Rated People and a damp expert should contact you to diagnose more fully.
Peter Barber CSSW. CRDS.
London Waterproofing Solutions.