No, not really. French rules mean it's quite hard to be a guide if you're not qualified, which is entirely different!
It's European rules that mean you need to be qualified, however some French regions decided that only French Qualifications were valid.
No, no and no.
The European rules do not give people the right to take qualifications accepted in the UK to other countries. The fact is, there is no legal requirement at all to be qualified in the UK (unless working with kids).
The rules do allow qualifications which are EQUIVALENT to those in other European countries to be inter-changeable. With some justification, the French don't consider the few days training required for an MBL award to be equivalent to their own or other European training schemes. British guides who do hold an acceptable British qualification are perfectly legal to work in France. There are a few out there (e.g. Gareth at Endless Ride, Jamie at Ride the Alps, Jules Fincham and, very soon I hope, me!).