We go away every other weekend, usually within a couple of hours drive from glasgow, so perthshire, argyll etc.
We have between us :two work phones on Vodaphone, a personal iphone on 3, an iphone on EE, a mifi unit on 3, and old o2 sim. I can honestly say that it 'depends' hahaha
Not very helpful I know. I'm surprised at the guy in Oban saying Vodaphone is no use; if I had a gun to my head I'd say we've been more likely to get a signal with them.
The 3 cards were brilliant in France this year and we also had no probs in the states other than my mifi wasn't compatible with their frequency. The iphone with 3 worked fine.