In todays' Metro, there is a recipe for Pork chops in a cider sauce.
It stipulates FRENCH cider.
What's the difference between English cider and French cider ?
Can I use apple juice instead ?

Well one is cider, moi lovely and the other is cidre, mon petit. X
You can use whatever you want.
If you don't cook the pork properly it's irrelevant.

French cider is often sweeter and lighter than English cider, but that's a bit of a generalisation, because there are lots of varieties here and in France, of course. Basically just use English cider. You can use apple juice, but personally I wouldn't. The taste won't be right. The alcohol in the cider is what is going to give the sauce depth of flavour and a bit of bite to counteract the sweetness, even though you'll be cooking most of it off. I always add a splash of Calvados too. Lovely!

As Toby says though, watch how you cook your pork. It's horrid when it's overcooked, which is so easy to do. Don't be afraid of a hint of pink. Many people don't realise that the days when you were advised to cook pork until it resembled a toughened piece of leather are long gone, thanks to much stricter rules when it comes to the rearing and slaughtering of livestock.

Good idea - then throw the chop away!
I find pork chops or medallions the hardest to get right whereas lamb and steak are simple - because pink is good!
The best pork chop I've ever eaten was at a Jamie Oliver restaurant.
I couldn't believe it was pork it was so succulent.

It was the Normans who brought cider to the UK after the invasion of 1066. If I remember correctly, most French cider is produced in the Normandy/Brittany regions, hence the reason it came across with the Normans, and as you say it tends to be lighter, sweeter, and contains less alcohol than its UK counterpart. French cider tends to be @ 4% ABV.