when i upgraded from xl 30 to xxl 100 the lady over the phone checked my connection and told me with the new speed during the busy times or from 5-11 pm i may face speed issues due to traffic so my guess is using fast speeds are causing more congestion
---------- Post added at 17:05 ---------- Previous post was at 16:36 ----------
check out this post number 3 (at the 3rd page) about upgrading speeds
http://community.virginmedia.com/t5/...1105407/page/3