6pm to midnight is peak on Max, the control panel just records all traffic, regardless of if its peak or off-peak.
http://www.karoo.co.uk/broadband/fair_usage_policy.aspThe fair usage policy currently relates to the Karoo Max service only. The table below shows the number of gigabytes (GB) per month that maybe transferred during peak hours which are from 6pm until midnight every day.Your transmitted data should be very low with usenet as it requires very little and should not affect it much. I would suggest its something else. Started using BBC iPlayer or something?
I would not be worried just yet, I don't think anyone has been forced onto the new packages at the moment.

Mike