Welcome aboard Rob.
Obvious differences between UK & JDM Zeds are things like the number plates being square on the JDM Zeds, speedometers in kph (also limited to 112mph), badged as a "Fairlady" (instead of 350Z) and also they usually have aftermarket rear fog lights on the JDM versions as it is a UK legal requirement but not so in Japan.
There are though lots more differences (I believe there where 4 different specs of JDM Zeds available in Japan) including things like headlight washers to different spec brakes etc ~ have a read of this thread for some more info: http://www.350z-uk.com/topic/1648-the-differences-spec/