... i could just unbolt the steering column at the joint in the floor bulkhead and unattach above and inport an entirely new steering column which would mean i could leave ignition barrel in place and simply plug in and install yellow box,ecu, Transponder and change door and boot locks and job done!?
No need to go all the way to the floor if you go that route. There's another splined joint immediately after the rake/reach adjust mechanism.
So, you'd undo the 4 or so bolts that attach the adjustable bit to the steering column support rod ( runs from the 'A' pillar across under the steering column then down to the centre tunnel ). There's a bit more to it than that, but it's not too tricky.
This is a photo of the support bar with the steering column above it.
Here's the support bar off the car. The steering column reach/rake adjuster sits in the box.
Phase 1 cars have the support bar at the top, phase 2 at the bottom ( not that it makes much difference ).
Steering column on the support
That whole section can just be pulled off the bit of steering column coming up from the floor and moved to the other car. There's no fastening at all - it just pulls off the splines.
A bit too much clutter here I'm afraid, but it sort of shows the unit to be removed
I do have a spare reach/rake adjustment unit. I'll take a picture of it if you want ( I'd need to find it first though! ).
Hope that helps