Vodafone coverage had improved greatly in the Borders over the last year. But no matter who you go with there will be not spots. Plenty area will have no coverage from any network.
An I.T. guy was telling me about an "internet of things" sim that pick up any network. Don't know the details but might be worth a google
An I.T. guy was telling me about an "internet of things" sim that pick up any network. Don't know the details but might be worth a google