I've still got my original licence, the police don't understand them but as long as you have photo id (passport) to prove who you are then it should be ok.
I've never been stopped but my husband has, that's how I know. He was in a hire car at time and the police man after looking puzzled by the paper licence let him go.
Rumours abound about the amount of fines being issued so perhaps you'd better follow Spanish rules and have proof of your insurance. This is normally a receipt to show that the insurance is up todate, but in UK hopefully the renewal letter will do..
I've always been told that you need two triangles in car. If stopped don't remove your seat belt and if you're told to get out of car then make sure you put on reflector jacket before you exit.
Do not have your phone out in the car, keep it switched off and in glove compartment. It's also illegal for a passenger to use phone whilst you're driving. If you break down then you must use your phone when outside the car at a safe distance away.
Put headlights on inside tunnels and it's also illegal to wear sunglasses inside tunnels.
If you need glasses to drive then you should carry a spare pair.
If travelling on the motorway make sure you use your indicators when changing lanes.
Can't think of anymore rules but do ensure your valubles are safely hidden in car. Just have enough cash out for journey each day and put handbags well out of sight.
Have copies of ferry tickets handy to show when you entered country and return tickets.