i have looked into this extensively, at least with a 156. The manual ones MAY go lower, but i'm not sure on this one. All the electric ones go to the same height. Some people say the recaro's "feel" lower, but i've had people measure them from saddle to ceiling and they're all the same.
Jug, when i was doing my research i came across a post where I'm certain somebody did what you suggest and all they managed was a 13mm drop (or similar) because the seat starts to come into contact with the "bar" which is bolted to the shell. If you take the seat out and take a look you'll see what i mean - ensure you disconnect the battery for 30 minutes before attempting this as otherwise your airbag light will come on.
The only other option is nasty aftermarket OR you could buy a second hand seat and see if you can remove the height and slide mechanism and fashion something to bolt the seat direct to the floor pan - again I think clearance between seat bottom and floorpan here will be an issue so I'd do a visual check with the current seat in by sticking your head in the rear passenger footwell and taking a look, you won't be able to adjust the seat (except tilt) AND it's an MOT fail so you'll need to swap the seats out come MOT time.
Last edited by diddums100; 02-10-13 at 10:19.