Steve,
My point (tongue in cheek having read the posts above) is that if the FAA are happy to honour a piggy back as long as a license has the same NUMBERS (and don't bother about PP or CP etc. in front of them) .... well mine has the same numbers but is an NPPL not a PPL so is non ICAO (like a US Sport Pilot) and not capable of carrying a piggy back.
I was musing as to whether I could I just rock up holding it and the piggy back and if the numbers were the same whether they'd give me a check ride and let me out on my own. I am not about to commit that level of illegality anyway.
The next point was that the guys I am booked with didn't think I could book the hours as anything, for the reasons I set out above. .... and with which we both disagree.