I used to do damp coursing in a two man business that had to fold through failure to make enough money, the reason, well we used too much DPC fluid to make a profit in an industry very well catered for, for we used spirit based DPC fluid not Aqueous based that most others used because it was cheap. We also did not do the standard thirty seconds of fluid pumped in at 30 psi, we pumped the fluid in until we could see the damp of the fluid bleeding through the surface of the brick and joining between the two injection wand holes as a result our thirty year guarantee was worth something and in five years we never had a call on our guarantee, because our silicone damp courses worked, but we didn't make any money.
You see from what I have said above in damp coursing there are too many cowboys and the whole process is open to abuse, as to aqueous DPC fluid, you are pumping water in with whatever dilution of DPC fluid, and the dilution can be abused, as it is mixed on site so though it may look like a silicone fluid damp course has been injected, it could be a very lean dilution or even just water, as the punter is clueless and guarantees with many outfits are not really worth the paper they are written on as there are so many ways to dodge one's obligation.
But for an outfit to charge for a survey on a complaint of a failed damp course, just what is that saying, well to me having worked in the industry, it says they are doing their best to disuade a guarantee claim, they are attempting to dodge their obligation
So the only way forward for the typical homeowner is to seek advice, as to who to approach, well most DPC operators are members of trade bodies, approach them for advice, and with that the building/ trading standards department of the local council, then following that a solicitor.
But one thing I understand about working in the building trade for over ten years in various technical roles is that industry is rife with dishonest practices and I am glad to be out of it, as the deceit that is operated by many is astounding and from it I have learned, never buy a new build house, because I have seen how they are put together, it does not inspire confidence in something that is so expensive and of work on older properties, well an unclued customer is a gold mine to many