Kudos to @Steve_M for volunteering his esteemed colleague Lee to respond to my query. Happily the problem appears to have resolved itself, but I owe a debt of thanks to both gents nonetheless.
A credit to BT.
I suspect if I'd got my work laptop out during the delivery of my son 20 years ago, I would never have got anywhere near our 25th anniversary last year !
Keep up the great work guys - hope your line managers appreciate what you bring to the table.
Any of you chaps in S36 just suffered another 6023 problem? Turning it all "off & back on again" did the trick...hope it's not going haywire again 😞