Yes very true. I would say if you have the budget for a UK car don't even consider an import. On top of the spec differences you have difficulty of resale and poor residuals, as well as the fact that many Insurance companies won't touch them.
I've nothing againt imports per se, in fact I have owned literally hundreds of them, Skylines, Supras, 3000GT etc but an import Skyline for 3 or 4 grand is a totally different kettle of fish. When you are talking the thick end of 20 grand for a 350Z the vast majority of the buying public would not even consider buying an imported car, which makes them much more difficult to sell on.
I'm not having a go at anyone who did buy an import, I hope it doesn't come across that way. I'm just passing on my opinion as a car dealer of 20 years plus experience.