Michael Gardner
it will not be rising damp if you have a cavity , its sounds like when you had your walls drilled , the bits might have fell down to the bottom on top and in with the insulation, moisture could the to track across , form perhaps any holes in your pointing , all the out side ground being higher than inside walls, solution knock a hole out where the damp is and pull out some insulation to see if its wet , also check for debris , dorsetplasteringcompany.co.uk
