I upgraded to Fibre Optic with TalkTalk last year and the actual speed wasn't that noticeable. But in the past few months it has been dreadful. I can't even watch youtube videos without buffering all the time.
I have tried everything. Speed tests (speedtest.net etc) show different results all the time and are not consistent. I don't give them any credence whatsoever they are just a gimmic site to get ad affiliate commissions. I have 2 laptops and when I do a side by side speed test they I get quite different results.