A trip to Mr B's this morning yeilded the sight of his feet, and several hundred weight of BX glovebox bits.... This is the end result of half an hours fettling (and it locks with the key too!)
Will let you know about the little black box Mr. B
EDIT: - Dave has asked me to describe how I repaired the hinge in the hope it will serve to aid others...
Well, to be honest, it was quite simple really, but then I was very fortunate in that with what I inherited on teh car I bought and the 2 broken glove boxes I picked up from Mr. B's I had a complete set of 4 hinge joints for the lid and two hinge pins.
It would seem the hinge on the lid itself is the weakest link, breaking where it joins the lid body. By careful jiggling around I was able to align up the four parts of the hinge on the lid - I tacked them into place with my hot melt glue gun, before making a more permenant repair with epoxy resin.
Once dry I coated all the hinge parts very liberally in silicone spray lined everything up and gently tapped the hinge pins back home.
I have also taken the liberty of shortening the check strap (using a simple through bolt to limit its travel) to avoid over straining the hinges again. The result looks great from the outside and you have to look closely when its open to see the epoxy. Im not sure how long this repair will last before I resort to the piano hinge modification, but presently it looks good.