My guess is the aftermarket audio is there due to compatibility over here with the foreign unit maybe?
Most likely Ev0, but I'm sure it was English, as he said you couldn't enter by Postcode for the Satnav (same as mates Z4 2006).
It's not the language that's the problem, I believe import head units don't work out of the box with our radio frequencies, and you won't get RDS etc.
Also not sure how you can update the maps to uk ones (you must be able to thought I'd have thought).
.That'd make sense, as it was brought in 'properly' by Nissan wouldn't be surprised if they stuck a UK HU in there.
Out of interest has anyone said what Japanese model/trim level this car was? Does it have both Brembos and leather?

Sounds like it's an ST spec then, which is largely the same as a uk car I believe.