First, apologies for the delay in responding. We've had a rather busy Sunday during which I soon learned computers were low on the list of priorities
Thank you very much for so much info but it would seem my problem was lack of patience. I looked in at the Mac before going to bed (which was before you posted) and the ball was still revolving so just left it to get on... In the morning, it had completed all its tasks and was all ready to go. Seems the restart involved lengthier preparations than I expected. Also, I think being used to the MBP with its SSD has got me used to almost instant responses.
I've now started getting the licences and passcodes into the apps, which could take some time - I'm not the most efficient filing clerk
Edit to add: Revised signature is on the list