So it seems I did not enable the plugin.

Now I have to say that finding your way around Mach 4 is anything but intuitive so that is my excuse .
This is not helped by the simple fact that the manual applies to the 2014 version, and version 2 of M4 which has only been around since early 2018 has not yet had an updated manual produced.
So you try working through the old manual , and find the various configuration pages in the current version bear no resemblance at all.

Now while the functionality looks good in M4 with a lot of (maybe too many) options on the front page, and once you find your way around it may indeed be superb but I am still wandering in the jungle , and the guy who made the signposts, does not seem to have ever worked with M3 so they seem to be in a language much of which is foreign to me .
There is just too much on the front page . I cannot believe it would ever be used by the typical guy on a production machine

Obviously I have spent a lot of time on the forums in the meantime and there seem to be precious few who have mastered it, and I get the impression that most have stepper spindles , and those who have VFD control, or like me a DC motor with pwm are even fewer so constructive advice seems to be in short supply.

Doddy tells me that Linux CNC will involve a steep learning curve . I am wondering if Mach 4 might be just as steep.
Added to the fact that (it seems) threading will not be supported with UC100 so I will not be much further forward .

It seems that this device http://www.pmdx.com/PMDX-411 will cope with threading but is limited to 17 usable pins, so makes me wonder if I might be better saving myself a £100 on this and put it towards an ethernet device.

Meantime , back to playing with the wizards available in Mach 3 .
I have managed to string a few together to make some Knobs and tapers and stuff, but I guess it is going to be a while before I get to make stainless steel bolts to suit my mates old Ariel red Hunter