I had this latency issue. I didn’t get resolved, however I didn’t push as I moved to FTTP with another supplier a week ago.
In the end g3uiss, I had to email Paul Stobart the CEO and explain the whole situation and then he forwarded onto 4 people but complaints team did all the resolving of the matter. So went like
1) got a email from "complaints@zen.co.uk" saying that someone from tech team was going to call me next day ...
2) call was from tech team to verify that i wasn't using any sort of Wireless and send them the two gateways traceroute via live chat so they can copy and paste it for a ticket for NOC team.
3) email from Campins to say NoC team is looking at the matter and if i was to move over onto BTw, it will take up to a month)
4) email from Campins to say they was going to move me over from TalkTalk Wholesale to BT Wholesale and would be completed by 29th so end of month.
So will see how my FTTC line is when on BTw in middle of April when the 10 days is up for the DSLAM to recognizes line stability.