Hello @clarkej
I did find out why I can’t do what i want and some pointers to how it can be done.
Basically there is a good reason why standard fields cannot be moved around when customising a doctype. It’s because when this was previously permitted back around vers 5 or 6, it broke things quite a bit. EG if the Opportunity field is in position 80 on the Quotation Doctype and moved to position 30 then there is a chance that the form may break especially on an update. . The original discussion is here
Note - you can move any newly added custom fields as much as you like because these are personal to your install and will not be affected.
Personally I think there should be some feedback to explain why std fields cannot be moved when customising a doctype as ERPNext allows you to move fields , but just never saves the changes - there is no feedback that this isn’t permitted. Likewise the Documentation isn’t very explicit in this area.