Fearnt
I don't think you have any come back on C&G or the original surveyor 7 years on.
From what you have said, the survey you had through C&G was basic. You should have perhaps had a home buyers report which is more detailed but costs approx £500. This may have picked up any fault.
I would be tempted to get another opinion if there was doubt about what the buyers surveyor mentioned in the latest report. Get a local experienced builder in, to have a look and provide a quote for any work. A good honest builder may disagree with the surveyor. I dealt with surveyors reports for a banks Mortgage Dept for awhile and on a regular basis faults found in surveyors reports were disputed. Further reports were then conducted which cast doubt on the original surveyors findings.
If you get evidence that the fault is debateable, you could just place it back on the market or go back to the purchaser who pulled out with the contrary evidence.
Huckster