Firstly are you connected to Zen's own backhaul or BT WBMC?
You can easily find out within your account within the Zen portal
or by browsing to the following web site http://speedtest.btwholesale.com/
After the basic speed test completes (speed tester isn't that accurate) you should see two click boxes "Re-run test", or "Further diagnostics"
Select the second option and it will ask you to input your landline number, "Telephone Number of the broadband circuit:" enter your number
and run it , if you are on BTW wbmc backhaul then it should display a graph including your IP profile, if your throughput is below 40mbps on an 80/20 service it will trigger the option to run further tests, AKA TAP3 test I don't know personally what the threshold is for the 40/10 service but i would guess at something like less than 20 Mbps, if the second part of the test won't run, then you are probably using Zen's own network for backhaul
If you moved provider same address ordered same Openreach product ie 40/10 service the problem of peak time congestion would likely follow you as the SVlan would probably not be changed if using BT wbmc data transit, but if you are on zen's own, then it's very unlikely it would follow you( unless your new provider uses zen's wholesale for backhaul
Also, an engineer visit from BTOR will not fix the issues if congestion, but will likely result in a fee which zen will likely pass on to you
To get this sorted it's a case of pestering zen's support to sort it out
if it's a BTW issue then get them to pester BTW to change the svlan or another HOT part of their often overloaded network provide the TAP3 test results speed test results on their own speed tester http://speedtest.zen.co.uk/
Edited by tommy45 (Mon 01-May-17 22:02:05)