I joined Zen FTTC unlimited fibre 2 with a phone line for for gaming for low latency to gaming servers as they have direct peering for Microsoft (Xbox), Steam and Google Stadia), It was going great until i had a problem with the lon2/ixn xDSL gateway that was giving me the double of pings, Instead of 7ms, it about 18-21ms however this was a issue with talktalk wholesale side of things but taken me just a month and abit just to get them to move me over to a BT Wholesale (BTw) line that i originally on, and now ill be moved over to BTw at the end of this month.
Keep in mind, Zen will take out 1 month in advance when signing up (but this was done on phone sales) not sure if online is the same.
Talktalk (residential only) and Sky(including Now) are literally the only 2 Openreach providers that don't do PPPoE.
Do Sky do option DHCP 61/client ID still?
Edit
Tried going to Zen for SoGEA but they wont take of the line rental so still £34.99 without contract.(30 day rolling)
Also i did ask if get the "Digital Voice" would Zen provide me with the VoIP information so i could stick this on my cisco IP phone but is in there T&C that it has to be on there Fritzbox, so 7530 unless they giving out the AX version to new customers with Broadcom DSL chipset
https://en.avm.de/products/fritzbox/fritzbox-7530-ax/ If you need a Digital Voice with a number then AAISP is the best one with no restrictions and can put on a cisco ip phone (VoIP info will be on there customer panel)
https://www.aa.net.uk/voice-and-mobile/voip-information/ - Just remember, If you have a router that QoS compatible, Remember to let VoIP traffic for high priority traffic
unless Zen has this in place already or get there Fritzbox to do it via TR-069.