Silly me, the axles are not draw-out as I said in the first post, but are 1/2" in the centre section, stepped down to 7/16 for a plain section then the LH threads.
I say axles because I found another today. The same detail for centre section, but about an inch longer in the threads.
Alan you make a good point, but as Ian points out the best setup would possibly be LH on one side and RH on the other. I wonder how many owners struggled to get the wheel nuts off their Douglases, or indeed the left side of their Valiants!
Cheers
Leon