I"ve got a pay as you go dongle from 3, it was supposed to be £30 but got it free when I bought my laptop from PC World. It"s pay as you go so obv the best solution to your problem. I have used it while on the nightshift a few times, only ever put £15 in it and it"s done me for the past month or so. I"ve used it for around 30hrs+ and it"s still got credit left in it, these sessions include poker online & streaming video but not downloading anything.