Indeed Matt, it was the holes i measured. But if i gave backwards measurements ( quoted below ) and we swapped 'em round, the first socket posted by Bartelby by still wouldn't fit , but on the one i ordered, there doesnt seem to be a measurment for the pins. It just looks right and if it doesnt fit. i'll start again. I reckon Markbass, being a rather large company, can afford to have the components made as a one off so you have to have an official repair done
Dammit - just whipped out yon digital calipers.
15.85 mm length
12.35 mm width