The FT has a recent article on "Broadband can cope with surge in home work, says BT". It's interesting to note in there the analysis of a recent peak in traffic on the BT network, perhaps some unfortunate coincidences in timing:
"In an interview with the Financial Times, he [Howard Watson] said that BT did experience a record amount of traffic on its network on Tuesday night last week, when an update to the online video game Red Dead Redemption 2 and the release of Call of Duty: Warzone — a battle royale-style online game — coincided with Champions League football matches being played, including Tottenham Hotspur’s defeat to RB Leipzig."
I need to read up a bit more on the practical reality for end-to-end IP QoS. It's rather tragic that ultra low bandwidth but loss/jitter sensitive services like voice can be affected.