Bad Idea—let each one build a carrier—share costs and tech but not ships. It can only lead to problems.
The French and Brits have signed an industrial cooperation agreement on building their new carriers (2 for the UK-1 for FR).But the French have decided to postpone their decision to go ahead after 2010. Anyway, the carriers will only have limited commonality-the French ship will use conventional Rafale jets using steam catapults, while the Brit ships will have STOVL JSF variant.
This whole sharing business is for the “EU” fleet and is not a Brit-French thing .