Thanks for the above, if building up with weld I had only the option of mig repair.

It seems I have a side button Improved model D of 1913 -17.

I have learned something today however, on page 68-71 of Knibbs book BSA & Lincoln Jefferies it shows a trigger block patent No 30338 which is a double sear safety.
I have removed the trigger mechanism and it is exactly this but with one sear removed and partly explains why the rod has one notch not two but not why any of this has taken place of course. Obtaining a replacement of that and a correct piston rod isn't worth even attempting plus the cost, when the gun has no original colour to the overall steel, is not viable.
So plan A being of some kind of repair is the only course of action in this instance which will achieve a working gun (hopefully) but a fairly rare model spoilt.

And what I learned today? was the pitfalls of buying something you don't know enough about but this is exactly how you learn afterall.

Now unless anyone has the parts and cheap that I need to correct it (may do a separate parts plea thread) I will consider continuing with the bodge repair.
Further advice still very welcome.