You will have to put up a thread on that conversion, my colchester is like a bag of spanners.
What make/brand is your boring head Rory ? I have an indian one i picked, but i don't have much faith in it.
Making an ER32 backplate. Could have drilled and bored the ID but wanted to try holesaw on a 50mm thick part. It works, went 30mm deep on the first side then flipped. Quite slow because of chip clearance having to peck drill. I did not use a pilot as I want the centre for another part.
Fit a spare digital calliper to my imperial slide, no more random sized parts!