Tony: I was talking in nm, not ft/lbs. So 20nm = ~15ft/lbs. I'm still fortunate they didn't break tho!
You surely are, hence my feeling that if you were talking ft/lbs that your torque wrench needed adjustment or discarding :-) I was mislead because all the other posts were talking ft/lbs. I am glad that you are not facing buying a new Torque wrench.
I also think, given the trivial amount of money involved, that replacing the bolts is a fine idea.
May I offer a tip on clutch centering - beg borrow or steel a dial gauge and center that clutch plate as near as perfect as you can. Then when you fit the transmission to a clutch you know is perfectly centered, run the mounting bolts straight up to torque in three stages. I suspect that the manuals still have nonsense in them about leaving the mounting bolts slack, starting the engine and then engaging and disengaging the clutch - in my opinion a perfect way to ensure that your clutch and gearbox input shaft act like an epicyclic gear.
Why BMW didn't accept the 10pfennigs increase in manufacturing cost and allow for and fit a spigot bearing is quite beyond me. I suspect it was a Teutonic extension of the middle finger to convention.