I've already looked at that, but all I've found is Para 10, chapter 6, page 6. Which explains what to do for IFR flights. I haven't found anything there about VFR flights.
Not for that it's not there, something of an HD document, but I certainly couldn't find it - nor anything that mentions this subject at all apart from the US based document posted earlier.
So, the question remains, can I leave early on a VFR flight plan, and how early?!
Funny - should be a simple question easily answered, but clearly isn't.