Gotcha, I'm still a little skeptical that it's factory...unless it's a NY Taxi model. I've seen lots of euro models with rear seats but can't find anything about ones ever sold over here.
Either way, it sounds like you'll need to either get to the backside of the bolt and see if there's a nut holding it(likely scenario if seat is a home gamer install). You can remove the exhaust heat shields, they're just bolted in from what I remember seeing. Or grind the head of the bolt(s) off. Lots of noise and sparks doing it that way.