Who was it that had 4 seats in the back? I remember a post somewhere (can't remember if it was on here) where they'd had a bench made by some specialist to seat 4 kids in the back, fairly looked a tidy job.
The M3 rear seat should fit, don't know what it would do to the 'look' of the car without Alcantara... I suppose you could re-trim and whole rear bench and back out of a fooked M3 maybe...
Oh yeah, welcome back.