I wonder if that includes video sites like YouTube being "deprioritised"
Yes, they've clearly told me in emails that they do, which is fine within reason, all isp's do.
But that isn't the issue that several - at least - of us have been having on Sept 15th, and again on Oct 1st, 2nd, and again today. It's a complete and sudden slowdown of all downstream data, both international and domestic, and irregardless of whether it's http traffic or otherwise. I have graphs that show the sudden cutoff in speed and the just as sudden resumption of service as usual several hours later on each of those days. It has yet to resume normal speed again today, but I trust it will, probably at about 10-11pm tonight.