Buying first house with damp course warranty running out

[Hails]

Hi there, I'm in the process of buying an 1840's mid terrace and have had survey results back which have detected some damp. I spoke to the surveyor who advised the meter had picked this up and we needed to check a damp course was in place and under warranty. I asked where the damp was and was advised we wouldn't be able to see it.

On checking, there is a damp course in place which runs out in 2-3 years and I am concerned...
it may be faulty if damp is still present??
that we will need to replace it
that this will cost a lot!!!

Any advise would be much appreciated as this is our first house and we have been cleaned out with the deposit!! Does anyone know if the company the damp course has been done with (Dampco) will inspect it for free to see if there are any problems?

Many thanks!!! :D