Been reading this thread it was most interesting, so interesting that I decided to register just to reply!
For what it's worth:
Sky - Used them for 7 years rock solid, had my phone line cut outside by builders, spoke to Sky via chat, Openreach turned up the next day to replace the phone line and I didn't get charged for this. Jitter was very consistent, not sure how it would look with the current situation with so many people working from home. I only left them purely because for the same price I could get 350mbps download speeds from Virgin Media (there was an offer).
Virgin Media - Been with them for just over a year (notice given), absolutely terrible, jitter is horrific, amount of packet loss is crazy, customer services are useless, their 'technical' support is hopeless, their complaints department is useless, in summary don't waste your time with them, the only reason I went with them was for the download speeds, it wasn't worth the lack of stability, I had 8 days in a row of 'blips' while trying to work which was the final straw. Provided router is terrible (Super Hub 3), lacks alot of configurable things used it in Modem Mode only.
Virgin Media BQM
Vodafone - Had this for 7 days, so far so good, it's still in it's testing phase so DLM is still checking my line out, download speed is increasing with each 'blip' (overnight), a few spikes of jitter but nothing noticable in comparison to Virgin Media. The provided router is surprisingly good, the information provided from line stats etc is quite detailed for a ISP provided router. Easy to get credentials to allow you to use your own Modem/Router from Customer Services Chat. 24 month contract for £23.50 a month.
Zen - Had this for 3 days, it's still in it's testing phase so DLM is still checking my line out, download speed is increasing with each 'blip' (overnight), a few spikes of jitter but nothing as bad as with Virgin Media, the supplied router is good, a FRITZ!Box 7530, it's a feature rich configurable router, line stats information is quite detailed, static IP, 12 month contract for £34.99 (setup not included) & LIFETIME PRICE GUARANTEE - You’ll keep the same monthly price on your monthly bundle when your contract ends.