More of a heads-up than a discussion but just so you know, I have added a new section to both the Legal and Official Sites pages of Useful Links (click the link at the top of the page) which contains the link to a European Commission site (in English) which provides a wealth of advice and information on all things legal in the EU and specifically on the new rules which allow you to decide whether the law of your country of residence or your country of nationality will apply to your succession.
Mr H and I have written our French wills invoking this regulation. Some notaires don't seem as familiar with the law and how to write this as others, so search around. We have identical wills for our UK assets (property) so there's no conflict between the two.
But a question that neither the notaire, nor Google, seems to be able to answer: in the event of a death who administers the worldwide estate? The notaire will deal with France but how would they deal with transfer of UK property, etc.? Is it prudent to name UK executors as well? Whilst the theory that the notaire deals with everything is OK, in practice, how would it actually work ....?