With my Vodafone pay as you go mobile-Internet dongle I've used nearly 5 gig of data in almost one month. So my £25 for 15 gig looks like lasting three months. A fraction over £8 a month. Seriously cheaper than the £39 a month Talk Talk was charging. I've been a bit more frugal in my on-line use than before but I've never downloaded music or films and don't expect to start that now.

I gave up on using vnstat to track my data use. I asked on linuxquestions.org but got no result. I got a name using ifconfig and found a command that showed real time use, updated the database and got one full day's use using just the vnstat command. After that I got nothing.