Identifying cavity walls:
http://www.west-norfolk.gov.uk/default.aspx?pa ge=22399
There are a lot of scams out there although there are problems too. Wall ties before 1930 were not galvanised I believe.
Aparently typical signs of failure are horizontal cracking of mortar about every 6 rows (iewhere the ties are). Obviously bulging walls too but if you had that I doubt you'd be asking.
I'd guess your survey probably just entails him knowing that there are houses in the area with the problem. If you've cavity walls then you'll likely get the problem at some stage so he probably doesn't see it as a scam - you might disagree!
I used to own a 20's council built semi detatched houseone of many on an estate solid walls as evidenced by the condensation. This didn't stop someone paying for Cavity wall insulation to be put it. They got a nice neet little set of holes drilled and filled with foam!