If the surveyor had some decent experience and training and we didn't live in a sue-happy society he would have said the moss might be doing some damage so you could have a look and see though its probably not anyway and the roof will probably last another 5/10/15 years or whatever. But unfortunately homebuyers surveyors really are a waste of money and we do live in a sue-happy society so the poor little dopey surveyor cannot write anything else. You seem intent on replacing the roof anyway, have you actually been up on the roof and actually peeled away some moss to have a look? You haven't even given us some decent pics to comment on. you will find numerous websites on the web and threads on here where the conclusion is that all of the lower end roof finishes are much of a muchness in terms of reliability and longevity provided workmanship is good.
