Can you give us some more info regarding his boat-buying, e.g. budget, fuel preference. Some of this may require some research in the south of France, e.g. fuel availabilty, local engine service centres.
Regarding qualifications, if he lives in France I believe there is a system of compulsory testing depending on the engine size. Alternatively, he could obtain his ICC (International Certificate of Competency) in Britain by taking his Powerboat Level 2 or above. More info on this can be found on the RYA site.