I've done some more investigation into ver 3.6.6 by fudging the exit of the setup url.
Substituting?? [ m_cmd = "run pcb-gcode-setup;\n"; ]????? for?? [ m_cmd = "run " + g_path + "/pcb-gcode;\n"; ] allowed me to bypass the space in my user name.? (this is allowable in Windows, so must surely be a ulp language problem??). ?
The setup url now runs, but has a really odd (and annoying) problem whereby changes to machine setup (in version 3.6.6) are not saved in "C:\Users\Peter Harrison\Documents\pcb-gcode\Settings", but instead appear in the settings folder of my earlier version 3.6.2.4 which is located in "C:\Users\Peter Harrison\AppData\Local\Pcb-gcode".?
I guess I'll still be using ver 3.6.2.4 for a while!!
Hope this is useful information.
Peter H