Thanks again for all the replies. I went back to the ANO after reading some of the quotes from it supplied on this thread. The only part that seems relevant is this...
Personal flying log book
79 (1) Every member of the flight crew of an aircraft registered in the United Kingdom and every person who engages in flying for the purpose of qualifying for the grant or renewal of a licence under this Order must keep a personal flying log book in which the following information must be recorded:
(a) the name and address of the holder of the log book;
(b) detailed information about the holder's licence (if any) to act as a member of the flight crew of an aircraft; and
(c) the name and address of the holder's employer (if any).
(2) Detailed information about each flight during which the holder of the log book acted either as a member of the flight crew of an aircraft or for the purpose of qualifying for the grant or renewal of a licence under this Order must be recorded in the log book as soon as reasonably practicable after the end of each flight.
..and the definition of flight in the ANO is this:
Meaning of in flight
256 (1) An aircraft is deemed to be in flight:
(a) in the case of a piloted flying machine, from the moment when, after the embarkation of its crew for the purpose of taking off, it first moves under its own power, until the moment when it next comes to rest after landing
So I'll leave it in my logbook for my own benefit but tippex out the time so it isn't counted as flight time or for the issue of a future license.
I maybe should have said in my OP that I have a PPL, and that the checkout was by a group instructor to fly their aircraft as PIC.
One comment for the OP that nobody has mentioned - the attitude that the club / POH has set a xwind limit, and that if it's 15kts you will fly, 16 kts you will not.
As I posted earlier the POH does not set out a limit but it does say that an average pilot can operate safely upto 15 Knots. This is not limiting but a recommendation. My groups policy is however limiting and I will respect the owners wishes when operating their aircraft.
Since I only have 1 hour PIC on type I don't consider myself above average!
As to this being an arbitrary number; aviation is full of them, whether it is in the definition of VMC/ IMC or licensing hour requirements etc. I agree that these are arbitrary numbers but they have been set out for our benefit based presumably on others past experience or hind sight.