The most important point is that you must have the right to live and work in the country you're thinking of. If you have an EU passport, you may live and work in any country of the EU.
However, to work as a pilot in the EU (and the other countries of the JAA), flying EU-registered aircraft, you must have a JAA licence. Unfortunately, they don't make it easy to convert other licences to the JAA one! Similarly, to work as a pilot in the US flying N-registered aircraft, you must have an FAA licence and a green card.
While it's true that countries within the EU will want you to have a good standard in their own language, they cannot enforce a national-only employment policy. Such a policy would be illegal, but there aren't many non-French in Air France, nevertheless!
There are many countries in Asia and Africa that will employ suitably-qualified (ie, experienced and type-rated) graduates of either the JAA or FAA systems, as they don't have the training infrastructure of their own. Korea instantly springs to mind, but there are many others.
Incidentally, Ryanair is Irish, not British.