On Sundays, pay at pump can be all that is available in areas off the motorway. Not all UK cards work in them either.Avoid the pay at pump unless you can avoid it in France.
It's standard practice with pay at the pump in this country too. When you see the bit that says "begin fuelling, max spend, £99" - that's because they've authorised (not debited) £99,and then the correct amount is debited afterwards. And there's usually a stick on notice that says, if you use a particular card type (can't remember which one) , they recommend you fill up with at least £20, as that card type doesn't release the authorised funds straight away. That's what happening in France, but with the added complexity of it being a cross border / currency transaction.
I forgot too. That will be your Spanish bank taking money away from you so you have to pay them interest or they don't have to pay you interest whilst they make some for themselves.
France is economically screwed until it sorts out the 35hr week, 2hr lunch and striking at the drop of a baguette. It's still ten times better to live in than this shit hole