Nothing wrong with imports, plenty here have them but they do come with a variety of specifications. Normally they can be spotted by the square number plate at the back although you do see the odd one with a U.K bumper. Specs on U.K cars are fairly easy to spot, I always look at the steering wheel, 6 buttons means its a GT, 3 buttons a non GT, and there are very few Nissan options other than trim, colours, SatNav, spats, maybe a couple more? plenty of aftermarket ones though . If your budget is around 11k then you're looking at a 54/05 possibly 55 reg'd vehicle. The Zed was given a facelift and a bit more power for 2006 and these tend to cost a bit more. 55 and earlier models do come in the cheaper road tax bracket though .
Look out for the service history, very important that the work has been done on schedule, a car with 50k should have had 5 services minimum, walk if the book has been "lost". The car also has a few minor issues, the bose CD skips tracks when cold, the gear change from first to second is clunky when cold, the back axle clicks now and again especially if its been standing for a few days and as you've already noticed the seats do start wearing after a few years. From a personal point of view I'd also avoid one that had a mountain of previous owners. Other than that, just the normal things you'd look at on any car. Some dealers tend to throw on cheapo tyres so take a quick peek at what's on the car. The 350Z though is a very sturdy car that provided its been well cared for will last for many years, take your time, the right one will come up soon enough
Pete