I have a pay as you go o2 dongle which we have used when in the middle of nowhere. It's something like 2 quid a day or something, which is fine as we don't use it often, but am willing to pay that if I need access that abdly (DH has to chekc emails when away) It cost 30 quid to buy from o2. I would call your mobile phone provider as I think I got it cheaper because of my contract phone.
Not sure on solving problem, I thinka s long as there is a phone signal you are ok...but is there a signal...!
I would get one anyway if you are unsure. It wasn't that expensive and costs nothing while it sits in the laptops pocketk, but when we go to races or wherever I can log on and mooch on MN or check emails from the comfort of my car!
Plus handy for camping and visiting friends/family with no internet