Some countries require a certain minimum remaining period on the travellers passport, mostly in connection with the issue of visas. Assuming you are a UK passport holder, I cannot imagine that any EU country would bother if another EU country's passport has two months still to run. At most you might be asked how long you intend to stay, especially since you will be entering the Schengen area of which Britain is not a member. An airline will want to see a valid passport and might hesitate if it is to expire before the return journey. If you want a difinitive answer then speak to both the French Embassy and the carrier you are using to cross into France.