I'm not disparaging the OP in particular, and respect his 40 years experience as an electrician.
But I would suggest his experience does not extend to this particular work. I have read on here and other forums (and not just electrical work), where people ask quite searching questions, on the pretext that the work will be done by competent persons, where it fact they intend to do it themselves and are after guidance on how to proceed.
I may have that completely wrong in this particular instance, but others here seem to have formed the same suspicions from the OP's reply. The OP hasn't replied since being questioned as such, so the suspicions may have some foundation,
If I was in a similar situation, however tempting and indeed satisfying it would be to carry out the work in my own property, I think I would leave all the supply and installation to someone who is competent to do the work. If I couldn't resist the temptation, I would be honest enough to state my intentions & seek advice from members here, and be prepared to suffer censure. It is of no particular criticism of the OP here, but just because he is an electrician of 40 years service, we should not be afraid to recommend the same, as we would do to someone else who is not competent.
I hope the OP has his consumer unit installed in his workshop satisfactorily, and enjoys his retirement.