Things moved on again today, and I was privileged enough to visit Ultrascale's engineering workshop this afternoon to collect the axles that I had ordered only last week:
This is one of the fortunate things about living along the way from them (actually, a few miles south) - they give you the option of coming to collect your order personally when it's ready.
These axles are from their standard range: the 1/8" driving axles (on the left) are in fact meant for British engines with outside frames / outside cranks, but can be usefully employed, with maybe a bit of trimming, as axles for 21mm gauge driving wheels.
The 2mm dia. bogie axles (middle) are also turned out 26mm long. You can specify this at time of ordering, and it gives you the facility to trim them back if they are a bit long. Much easier to do this than find your axles are too short.
The 2mm dia. pinpoint axles (right) are the standard 28mm long, as used in 21mm gauge anyway. Again, Ultrascale give you the option of specifying this when ordering.
By using standard Ultrascale products, not requiring anything of new design to be made, this can speed things up considerably.
All we need now are the wheels themselves, a back-to-back gauge, and some High Level hornblocks and bearings!
THOUGHT: it may not be necessary to buy a back-to-back gauge immediately, as Stephen Johnson's helpful diagram suggests that a maximum back-to-back of 19.92mm can be used for Irish broad gauge......