JDM = Japanese Domestic Market, so yeh its just an import. IIRC they don't have abs, or airbags, and are set up a little stiffer, compared to the Uk spec car. Also slightly up on power, and havce different wheels.
Not exactly sure on running costs, but i would have thought they would be similar, probably best to try and find a dedicated ITR forum, or pop over to the honda section on pistonheads, and ask there.
If it were me and i was hoping to run it for three years, i'd defiently be looking at a jdm car, or a more expensive lower mileage uk car. Depending on your mileage a year, I would have thought starting a 3 year ownership on 140k, would mean the car will be a dog at the end of your ownership.