You must have your medical dossier with the Authority which will issue your licence (Aircrew regulation requisite). If you want your licence to be issued by another Authority than France, you'll need to have your file transfered.
I took me 14 months to have my dossier transfered from Belgium to UK CAA. I had to translate several reports into English, and the CAA kept on leaving me messages on other people's voicemails to get in touch with me, it seems they can't write emails.
So leave your medical dossier where it is, and I don't think you'll have problems to have your licence issued by the DGAC on the basis of tests or training done elsewhere. The DGAC reads English, they even wrote in English for me.
UK CAA is all paper, nothing can be done through a website, it takes weeks (5 weeks for me) to have a licence issued, it's incredibly expensive, they don't seem to be able to write English (keeping trying to call me instead of Emailing) or any other language, and they don't seem to read any other language than English.
Last edited by 172510; 13th May 2013 at 21:35.