Dunno. It depends what you want to do in the future. If you want to fly for a UK operator then the national licence is fine. However, if you believe the pundits, you need a JAA licence to enable you to work anywhere in europe. The fact that most european national airlines (Air France, Alitalia, TAP, to name but a few) have made it perfectly clear that they will not employ 'foreigners' is, so far as the europhiles are concerned, beside the point.
Consider,however, that if you want the JAA licence, you have to take the JAA ground exams. This will mean learning a new language - european English, which, the JAA have insisted, is what the central question bank will be written in.