I had that exact problem when I was searching for a Zed ... to the extent that I actually lost £250 due to a dodgy comparison website not recording the details properly.
I entered the number plate and chose JDM import, but for some reason it hadn't registered that the car was imported ... so I went and put a deposit on the car and then rang up the insurers to accept the quote ... I explained it was an import and then they came back with a quote over a £1000 more!
I had to pull out of that purchase and lost my deposit ... but thankfully I got myself a UK spec not long after ... Happy Days!
You may have already tried them but I used www.GoCompare.com in the end and their online system does recognise UK Specs correctly...
Good Luck