Having tried for some 4 years to get a BP du Sud account closed and the balance transferred to our Credit Agricole account I decided to write to the Mediateur for the BP.
Almost immediately BP closed the account and transferred the money.
I assumed this was the end of things but yesterday I had an email from the Mediateur agreeing that BP du Sud had been unreasonable and that I deserved not only a proper explanation for the delay but also 300€ compensation.
They’ll probably ignore a letter sent by regular post. If you sent it using the LRAR service (Lettre Recommandée avec Accusé de Réception) then they have to acknowledge receipt and you’re much more likely to get a reply.