Hi markwmsn - here's all the info you've asked for:
iCloud photos 131,054 videos 3024 other items 70 - updated at 8.44
iPad Air 5th gen. photos 131,129 videos 3024 other items 1 Synced with iCloud just now iOS 16.2
iPhone 12 Pro photos 131,130 videos 3024 other items 1 syncing 1 item with iCloud (it always says that now) iOS 16.3.1
MBP 13 inch mid 2012 photos124,477 videos 2737 other items 1 uploading 116,247 items (it seems to have been doing this for ages) other items 1 10.15.7 Catalina
iMac 27 inch late 2009 photos 131,134 videos 3024 other items 1 10.13.6 High Sierra
The latest photo on the MBP was taken on 5th March 2023 and since then I've added 217 photos, according to the iMac. I was in New Zealand from 6/12/22 to 10/2/23 and that seems to be where the bulk of the difference lies.
I don't know why the MBP seems to be uploading everything and at the speed it's doing it it's going to take months to complete the upload, despite the fast fibre broadband I now have. Maybe once it's done that it will start downloading.
I hope this info might be useful. Might it be possible to start a new Library on the MBP - if so would I have to delete the existing one and how would I connect the new one to iCloud?