After the switch over from Bigpipe to 2Degrees Broadband as fibre RSP, I dropped from 200/20 to 100/20 and while a lot of effort was expended trying to lay that at the feet of wi-fi or router problems a couple of days later there was another brief (07:50am) outage and instantly on reconnection, with nothing locally changed, it was 700/400.

Just a note that greenfields, 2Degrees AKA Snap is brilliant, but if you've got an old crufty set of boxen and switches from decades of older tech, it's harder to drop something in without issues.