dpc firm want £75 to investigate guarantee claim

kuepper

Bought my semi about 5 yrs ago, nothing showed up in survey and vendor had a 25 yr guarantee for a dpc in the 'front , side and rear elevations'. having just moved some furniture it now looks like i've got rising damp in the side elevation wall. Contacted the firm who guaranteed the work and they say it'll cost me £75 for them to come out and check if it comes under the guarantee. When i asked why wouldn't it, they said the previous owner had to do some work - plastering, replacing timber - internally as part of their advice and if that wasn't done they won't be liable. I don't know if the previous owner did the work or not though the plastering looks fairly new, unfortunately the floor surface is laminate and so impossible to lift to inspect under the floor without damage I don't think.

Not sure whether to pay the £75 and see what the firm says (but it's going to be easy for them to blame the previous owner ) or pay another dpc firm or independent surveyor to do a survey, though the latter seem to cost about £300.Any advice?