Mate, I live in the North East too. I live in Stockton on Tees but Work up near Newcastle.
JCImports was one of the places I visited. The cars he sells are okay. you won't get leather or brembos from most of the imports but as others have posted you can save money and do that yourself. Other options are Vine Place sorts and Performance but they are not cheap. You won't get one for less than £16k. A1 Sports and Performance ocasionally get the odd 350Z too, but mostly still Supras,etc. To be honest, you won't find a 350Z for less than £14k, if you do be careful. Also most of the ones advertised on AutoTrader etc for low prices aren't anywhere near the UK yet. you'll have to wait weeks to get it and it'l need fully converting too.
Without exception all the imports are still badged as the FairladyZ so you will have to remove them and buy new badging. Also most imports have no rear spoiler which really affects the aesthetic look of the car. They can be sourced on this forum easily enough though but you'll have to paint it to match and fit it.
I would advise you to buy privately from someone in the UK who themselves bought an import and are now selling. That way they will have hopefully rebadged it, added the UK bits etc and will more importantly have some UK service history to ease any future pain and keep the residual up.
I did this. I have a black 350z (best colour in my humble opinion). It's an 03 reg. It was imported in 2004. Since then it has been rebadged and has rear spoiler but more importantly once in the UK for a while they can get UK Nissan Dealer history. Also a buyer can then see loads of Uk receipts,bills,etc. I still haven't got round to putting leather or brembo's on! The brakes are fine in normal conditions (I use the car to go to work, don't use it for track days!) and the velour seats are fine. All you care about when you drive the 350Z is the DRIVE! Solid, heavy feel through the geers, sharp responsive steering,looks to die for.
If you buy an import from a pivate seller you stand to get the best of both worlds. A cheaper 350Z as its an import but also the pece of mind of a car that has been looked after and has recepits,bills,etc from a UK Main Dealer which will help residuals when you come to sell).
Good luck mate. I've owned Evo's and Supras,etc bu the 350Z is a real throwback to the old muscle cars and a real head turner. You won't regret buying one. X