And based on the reality that seems to be you are testing over Wi-Fi suggests that maybe changing router and moving to a confirmed 802.11ac 5GHz service might fix it.

Until you show that the problems are also present when connected via Ethernet you will be stuck with them trying to fix a wi-fi problem.

What?

Whilst I have done some tests over wifi I am complaining about wired tests maybe I sent him a link to the wrong one, but frankly it makes no difference as wired is the same

Sorry in that case, if Ethernet is showing slow speeds then yes likely to be their network

NOTE: We started seeing this en-masse back last November, when we were told it was our tester that was broken but nothing our side pointed to that, and then then in April there was some improvement for a lot of people. So getting call centre to admit to problems will be difficult.

The line that The Register got told (in March if I recall) was that line cards needed updating and CDN content was affected, by line card believe they mean the cards in core network devices and the CDN aspect is odd since our speed test files are not delivered over a CDN