This explains a lot better than I can... http://www.smstextnews.com/2008/10/virgin_mobile_has_no_business_arsing_about_with_mobile_broadband.html

If anyone's on one of these capped ISP deals check out NetMeter 1.1.3 . freeware, See how slow/fast your connection is AND most importantly lets you set notifications for a total data limit per day/week/month. I've used it for years and it even works on bloody vista 64.....

As great as that is, it doesn't appear they have any Pay As You Go offerings yet so to be honest I'd rather just go to T-Mobile instead. I don't want to be stuck on an 18 month contract for something I'd only use every so often. Shame really as being a Virgin Mobile PAYG customer I would have got one of these if it was also on PAYG. Rob