Alternatively use a 3G router. Vodafone (or, at least, my local Vodafone shop) had a deal last week where they gave you a 3G Wifi router for €20 but gave you €30 euro of PAYG credit. I checked that they would take it back if coverage was bad. Actually coverage is great and I'll be keeping it, but I'm using it in the sticks and my experience of 3G performance in the Big Smoke is much worse.