I agree with the others on here, it almost sounds like the torrent program not set up or fine-tuned as well as it can be.
Try these suggestions:
1:) Download a different torrent app (not the portable versions) try the latest qbittorent or uttorrent release (I prefer utorrent much more stable than Qbittore)
2:) Set up the port forwarding properly and while the torrent programs open use canyouseeme.org to double check the ports open
3:)Turn off uTP fully, usually called 'enable bandwidth management uTP' under bittorent section settings in uttorent program and if you really want under bittorent is an option called 'protocol encryption' set this to =Forced this blocks any isp from knowing you are torrenting.
4:) Reduce your upload speed by even 30-40% and your download speed by 70%, otherwise line will become unusable during surfing.
5:) Don't try to separate download folders to temp or multiple folders, stick to one download folder (usually defaults) but put the download folder onto
An SSD hard drive, if its on a mechanical hard drive this can cause instability, caching issues and even speed drops.
Now try queuing up 3 version ubuntu torrent files from here:
https://ubuntu.com/download/alternative-downloads
You should get almost full performance with those 3 torrents just do the test during early morning or afternoon not 6pm-10pm (peak times)
I have not seen any sign that Virgin media are traffic or shaping torrents or openvpn or any other protocol but could be wrong.