Just as a footnote to this trip, I took a lesson how to ride in sand today in Dubai. Still damned difficult even on the right bike for the job, with the right tyres, at the right pressures.
Everything is shouting in your head to slow down but, as I competently demonstrated a couple of times in the first ten minutes, if you do you're going to stop half way up or come off at the top of that dune!
Eventually got it going pretty well but after less than an hour I was completely worn out. Fat and 54 or not, I now have added respect for the Dakar guys who do this sort of stuff all day for 14 days. Damed impressive.
Need to get fitter and get back here again.