Section 35, Part 4 of CAP393, the UK ANO, which is about Personal Flying Logbooks:
3) For the purposes of this article, a helicopter shall be deemed to be in flight from the moment the helicopter first moves under its own power for the purpose of taking off until the rotors are next stopped.
My interpretation of the above quote is to log time only from when the aircraft begins to ground taxy, or when you raise the collective to lift off, in a skidded aircraft.
As an military trained pilot I always previously logged as per the military rules (same as per the UK ANO). Now, as a UK licence holder, I have always logged as per CAP393. Thirty years worth.
In my present job, and many others, operating from an airport, logging from engine start would add up to another ten minutes or more to many flights. That's possibly an extra ten to fifteen percent. I was always taught to fly for quality, not quantity.
As long as folks are honest in job interviews about this or to the CAA, (never mind about when shooting a line in the bar), and I'm sure you would be, should the question ever be asked, what the heck.