There is upstream management in place on most tiers. So whilst downloading from FTP or similair is not capped at all, anything that uses your upstream heavily (torrents, file backups, streaming TO Twitch) can tip you into traffic management.
If you look on the VM traffic management guide HERE and expand the table by clicking where it says "show more details" then you will see "Section 2: Traffic management to optimise network utilisation (what happens during busy times and places in addition to traffic management as described in Section 1)".
Here they list what traffic type is managed and Peer to Peer (Bit Torrent, etc) and Newsgroups are slowed down during peak hours. The table lists peak hours as "Weekdays: 4pm until 12 midnight Weekends: 11am until 12 midnight".
This is separate to any restrictions triggered by exceeding the upload thresholds so always applies during these peak periods.
Disclaimer - I don't work for Virgin Media. I'm just another VM user trying to help out so my answers may be wrong If my answer solves your problem please mark it as helpful as it may help others My setup: Vivid 200 Optical fibre with Superhub 2 in modem mode connected to a Netgear R7000 router. Telewest/VM user since 2001.