Plain and simple, I've a 50mb plan, Speedtest shows 52mbish, downloads always capped at 5mb, never higher, whether FTP, HTTP, Torrent, whatever.
Why are my downloads capped? I can just about tolerate your DNS Hijacking without having my speed cut.
50 MegaBits per second (your Virgin plan) equals roughly 5 MegaBytes a second download speed. So you are pretty much spot on.
I think ISPs use the megabits speed in their advert because it sounds faster.
Explanation of megabits and megabytes here: http://www.ispreview.co.uk/index.php/2015/04/confusion-broadband-isp-speeds-megabits-vs-megabytes.ht...
OMG, I like to think I know my computers, use Windows and Unix, 34+ years plus, and this one went straight past me!!!!
*Note to self* Must read the small print properly.