Also remember that many filling stations are self service in the evening and during the night off the autoroute, and they don't like uk cards.
I've not had that problem for many years now - we do tend to use a Caxton Euro currency card, but have had no problems with the Barclays debit card, Amex, etc.
Used to be a hassle a while back before we went chip and pin, and sometimes the instructions are not as clear as they could be.
As an example, we followed a Brit car into a Carrefour station one evening. Automatic pump, guy got out shoved his card in and then stomped off. I drove in, and he stopped to say that "it don't take British cards, mate". I said thanks, stuck the debit card in, read the instructions (how much fuel do you want, pin number, go) and filled up. I then showed him how to do it and he was much happier.
Quite a few seem to want to know how much fuel you want to put in first, and I guess that catches some out. I always bung in 100, and when it's full and I hang the pump up, check the receipt against the pump display - never had a discrepancy or problem.