To those who claim it's an OpenReach issue that affects all internet provides: while it's true that everyone offering DSL services is renting BT phone lines which are owned by OpenReach, and that OpenReach did cause issues for all providers in the past, this particular problem in south east England is a problem strictly at Sky Broadband (of whom NOW is a subsidiary, the NOW broadband service is provided by Sky), so it's just Sky and NOW.
Other providers like EE, PlusNet, Vodafone, etc have not have any issues.
The curious could also have a look at Downdetector, and looking at the proportion of reports above the baseline (dotted line), e.g. Sky vs EE, BT, Plusnet, etc
The two claims that it is Sky and it is OpenReach are not incompatible.
An Openreach fault on the trunking from Sky to the wider UK internet would give exactly the symptoms, and the failure patterns, that were being reported.
But who is claiming it affected other ISPs, and where is this claim published?
Some users were claiming that all ISPs using OpenReach were affected, and the NOW rep on the phone with me claimed the same thing, despite me pointing out that my neighbors in the same block of flats who use other ISPs are not experiencing any issues.
You know, that unworthy thought never crossed my mind 💷💷💷