Colin, thank you very much for your very quick reply, and information.
A question comes to mind: can it still be said to be an ISP issue when my bandwidth/broadband speed is so significantly higher than the iOS speedtest results, i.e. the measured download speed with speedtest.net is virtually...
I'd be grateful for some help, please.
I have an Asus RT-AC5300 router, working with a Virgin Media Superhub 3 (in modem mode) on a DOCSIS3.0 cable supply with an "up to 300MBps" speed. I have measured the speed at different times of the day, using speedtest.net, and the download speed varies...