Personally I think autotrader is a scam. I've never heard of anyone buying a car they saw in autotrader for more than a grand or two. People buy it (me included) when sitting in places like an airport with f all else to do. With my last car, low mileage, the only calls I got were from people that saw it for sale on websites.
The problem here is the mileage. It's a fairly recent mind warp that has got people thinking cars will die if the mileage is too high. The only manufacturer I know of that has issue with high mileage is Porsche. Engine requires a rebuild at 100k then it'll do another 50 to 100k.
350z problem has a good 200k in the engine if it's serviced regularly. Only a guess as we'll probably never seen one with mileage anywhere near that.
If I lived in the UK and was looking for a Z I'd of bought this one for the original asking price without a second thought.
Just had an idea. Search the web, find a few Irish importers and give them a call. There's a good chance one might take it.
Guy