Posting this in case anyone else on O2 UK has seen the same.
Setup:
iPhone 15 Pro Max on O2 UK with the O2 Satellite add-on active
Was running iOS 26.4 RC (23E244), then later updated to 26.4 final (23E246)
Carrier bundle updated from 69.0 to 69.1 via the usual "Carrier Settings Update" prompt...