Skyyacht
"Please feel free to correct me if you feel that I have mis interpreted the JARs."
Indeed I shall . . .
A 'proficiency check' is a precisely defined test in relation to JAR-FCL. It can only be carried put by a JAA examiner (FE, CRE, TRE or IRE) for the purpose of revalidating a class, type or instrument rating.
A flight with an FI to check someone out on a new type of single-engine piston could well count as the 'one hour training flight' as long as it's at least an hour long as it will cover the sort of things that should be done like PFLs, stalls etc. However, the one hour training flight must be in a SEP (or TMG if a TMG rating is held).