It has been a requirement of ISPs for several years, with an enforcement and fine system in place from June 2017 until September this year
, when they seem to have concluded all big ones are complying reasonably. Like MrSaffron, I can't quickly find the original edict.
I'm fairly sure BT Consumer have similar to Plusnet but maybe not as good.
I don't know if any such terms are in place on Business products. Many T & Cs are different for those. Businesses are supposed to know what they are entering into on contracts. Not reading the small print because it is too complicated is not an option.
My broadband basic info/help site - www.robertos.me.uk.
Domains, site and mail hosting - Tsohost
Connection - Three 4G, tbb tests normally 35-45Mpbs down, 65Mbps off-peak, 9-24 up.
"Democracy means simply the bludgeoning of the people by the people for the people." Oscar Wilde