Look up ........Cough!
They've got you by the proverbials and there is only one thing to do.
Get a French JAA PPL issued on the basis of your UK licence. The french will accept the french class 2 medical, won't they. You do not have to give up your UK PPL which has been issued to you for life.
If in fact your UK licence is a JAA one then transfer the administration of it to France.