I've had similar worries out on the country lanes around here (as has BF). I always carry a phone (and try to remember to keep it charged). And I always carry $20 at least, pluss my credit card. Not sure who I would call though. I don't have AA and a taxi wouldn't be able to take my bike and BF doesn't have a car.....I do always carry spare tube, tools, patches and pump too and have needed them once when I had a puncture.

On long rides, I try to at least occasionally let my route intersect the train route. Which is what I did on Tuesday when the weather was much colder than I had anticipated and the headwinds stronger and I couldn't face another two hours of painfully cold toes. I made my way to the nearest train station and took the train home. Luckily, around here there are lots of train lines, and lots of stations. I rarely have more than 10mi to get to a station from anywhere, usually not more than 2 or 3 miles. And every village has at least 3 or 4 pubs, so I can always find somewhere to duck into to warm up and dry out if the weather is really horrible.