Well, the IMC is not a JAR rating, so you do not need it. It may be good practice though, as mentioned before.
The night qualification is not a rating, no test, just the requirement done with an FI.
Generally, a JAA PPL is done by people who don't have to worry about how much they spend of for sentimental reasons, as you will loose it upon gaining the next higher licence (not sure if you can keep an IMC?).
Usually, people do an ICAO PPL (anywhere outside JAR), that comes with a free night qualification (FAA springs to mind, but not only). The money you save on that could be spent on IR training (I don't mean the rating) or just extra hours.
Why limit your experience to just one island? Airlines don't do that either...
cheers IP