Now I do not know how true this is, but I have read a couple of reports that The French Government have printed certain GB stamps.
The report in question concerns the Windsor Castles Recess pane from the Centenary of Aerial Post prestige booklet which was issued on 9th September 2011. This pane was reportedly subcontracted out to the French Government Printer who operate under the Phil@Poste title (previously ITVF)
It seems that Cartor have entered into a relationship with the French Government Printer to fulfil their intaglio/recess requirements. If this information is as I say correct then this is the first time the French Government Printer has printed postage stamps for Royal Mail.
Looking forward to all your replies.