As I started this thread, a quick update in order - although I'm not quite sure what to say.
Some minutes performance is terrible (even on a threaded speed test) and then minutes later is is back to looking ok.
I'm sure that performance isn't as good as when I was on Sky, but that is only a feeling. Things worked back then so I didn't really have the need to monitor things. I do have a Sam Knows white box, so I shall look back over the graphs it generates and see if there is a noticeable drop in performance.
Also worrying, is that the targeted ads on Facebook for ebay show something things I have been searching for, and some other seriously dodgy stuff, and just weird random stuff - barns, bitcoin mining stuff, etc. I guess that is based on my WAN IP address, as I don't see the same dodgy stuff when I use my Surface at work on the wifi there (thankfully!)
Sky avg downoad speed was 36.6 in Dec, but since switch to vf it has dropped to about 32Mbps according to SamKnows. Although the number of tests carried out on same days over the festive period was very low (more people in the house, so I guess more internet usage). For 2 days when I was at work this week the min test results showed 15.0 and 13.1Mbps, but also a max of 37.2Mbps on the same days, so pretty variable. On those days I was here pretty much only to sleep - no real internet use other than my phone checking for emails, etc. Certainly no large ISO downloads or streaming of TV programs.