Plug was most likely removed to gain access to timing mark, to check after cambelt kit was fitted, the plastic plug has clearly gone brittle, and fractured on removal, plug was most likely seized solid! As the gearbox is being replaced in early October, and I'm guessing by the same garage, then what is the point in replacing it

I'd think twice about going back and complaining, just ask them to fit a new plug, if the exchange box doesn't have one!
Expect things to break on old cars!
well the box is being replaced on 2nd October anyway, the fools.
I am quite annoyed at this garage really because the guy that owns it used to be a one man band and I took my cars to him all the time 11yrs ago, now he is some modern big enterprise with apprentices and stuff and i think perhaps he has let a young twonk at my car?
They did the cambelt on it and its come back with a wobbly crankshaft pulley which is making a ticking noise and a sheared off plug hole!!
ive gotta go down there tomorrow by myself and argue that they have caused this because it had neither issue before it went in!
Thom