I rather think this is unlikely to prove to be a problem, particularly if the passport and nationality of license match. Probably the best way to handle this would be to decide at an early stage which car hire company you intend to use, contact them direct, explain the situation and ask for confirmation that no complications are going to arise for them - remember that the police, etc. are only going to be interested in seeing a valid license, any valid license (if the situation arises, but that would however have to be consistant with the driver's insurance). Once you have confirmation this is going to be accepted, make certain you note the date, time and name of the person you spoke to - if this is done by e-mail then you have an even better record. If you are going through an agency, including the likes of Holiday Autos, then they will need to contact their partner company in the destination country. None of this should be difficult to establish - European licenses tend to be more or less universally accepted as is the fact that people move around a lot.