A lot of aeroclubs cannot sell fuel to outsiders because they operate under some “sporting body” tax concession which disallows this.
In practice what this means is that if you turn up and “speak their language” they will fill up your plane while pretending to fill one of theirs (for a cost plus say 10%) but if you are a “foreigner” they can’t trust you to keep your mouth shut, so no fuel.
Obviously few people are willing to discuss this openly but examples are known in Spain, France, Italy, and even Greece.
No idea why, but there are a lot of places that seem to be finicky about selling fuel.
And if an aeroclub runs the aerodrome – common in France – then it is usually volunteers that will take time out of their day to come out to the aerodrome to fuel you up, and may live some distance away. If you land ’on the off chance" then the person you speak to might not know the procedure to fuel someone outwith the aeroclub etc…
No idea why, but there are a lot of places that seem to be finicky about selling fuel.
Some places sell it because they are business who make money out of fuel, some places use it for themselves and likely have VAT/Duty paperwork when selling to others maybe as it’s de-taxed?
Wherever you decide to go, I recommend you call in advance to see if they have fuel, to see if you can self-serve, and if not, when will “the guy” be there? No idea why, but there are a lot of places that seem to be finicky about selling fuel.
If you have a BP card, you can refuel at Carcassonne LFMK. Close too and they have a self-serve BP pump. I didn’t check notams, just VAC.
I used MC at LFMD a few times last year..? Has that changed then?
It’s an odd setup. There are two pumps. One only takes a BP card. The other takes just normal cards. But transactions are limited to €300, which may or may not be a problem depending on the aircraft. And my French debit card for some reason is limited to €150, which is a problem when you have a plane that takes well over €300 to fill up. You have to run multiple transactions, but you daren’t do one wing and then start a new transaction for the other one, in case something goes wrong with the second one and you have a plane which is too asymmetric to fly.
I have a BP card now, which makes life easier.
I used MC at LFMD a few times last year..? Has that chanaged then? LFNH has 100LL self service with MC – also a very nice spot. LESO takes MC on the western side
BP is often not accepted in France
I think it depends just on who the fuel vendor is. At Cannes LFMD it’s BP, so you need a BP card. A Total card will get you nowhere. (You can also pay with a regular card but you’re limited to €300). It’s true that every other airport I’ve refuelled at has been Total, but it’s not a very representative sample.
Haven’t checked the latest, but LESU pricing will likely be similar to LEAP. Note the restrictions on arrival times at LESU btw. You mention La Cerdanya. No fuel there for sale. For aeroclub only.
If you have Total Card you pay 2.5€/L, if you go via Aeroclubs you pay what shown in the machine +0.2€/L, if you use operations or trucks you pay +0.8€/L on top
It’s an option, it’s not necessary to have Total Card to self-fuel in France, it just removes the dependency on others and allow to pay less if you can fuel yourself…the deposit is 200€ (if you set annual consumption at 2000€ per year or less)
Without Total Card, it’s worth fuel in LESU same price but likely easier to organise with quick turn around versus France 
