Not too sure on what to make of this, Now Broadband BQM
The large increase in the green (minimum latency) suggests either a fibre break, with traffic taking a different, longer route, or possibly high interleaving being enabled.
High interleaving adds 16ms. Though DLM takes about a minute to resync to add interleaving.
The amount of downtime prior to the increase suggests something in the physical network going wrong, so likely traffic taking another route across the country for some reason.
It's almost certainly temporary and likely affecting all of Sky's network in that area.