hey mr nigel,
i only put in the tech log the time skids off the ground...
that is correct for tech log, but not for your personal log book.
either log ICAO/JAR - Rotor start to rotor stop or
log ANO/FTL - First taxi/lift - rotor stop,
its up to you (or maybe your company)
regards
CF
P.S. how you charge passengers is a red herring, charge them by any method you like !