I e-mailed Dave as suggested and had a reply from him very promptly.
His response has impressed me greatly and I am taking the liberty of copying the relevant parts of the e-mail to this thread.
"Our single set trigger castings can be fitted to the military receiver but it takes considerable work.
There is some tricky milling that has to be done inside the trigger guard, the hammer has to be slotted and drilled and a fly installed, the rear frame screw has to be replaced with a screw from each side, therefore, the side that is threaded has to be drilled and counter-bored, and finally, the holes in the trigger guard have to be tapped for the screws."
I now have to find a competant gunsmith here in NZ who will undertake this work for me.
If I am sucessful I will be ordering a set from him.
Sir Charles de MoutonNoir, this may be of use to you in your quest