I have a solwise 3g router and USB 3g with a magmount booster antenna on the roof. Total cost about £70..! And you don't need to piggy back on someone else's WiFi connection

See:
http://www.solwise.co.uk/3g-routers-3g-etr-9360.htm
http://www.solwise.co.uk/3g-datacard-to-antenna-adapters-adpt-026 ...