Indeed... That was exactly it.

Instead of the connecting link on the bayonet fitting pointing, smack on, at the 12 o'clock position (as one was looking at it face-on), it had been fixed at '11.57', so consequently when the cartridge was fitted to the arm or sitting on a record, it was 'drooping' down to the left at an angle, resulting in azimuth being out by a good millimetre and a half!

I should hopefully be hearing today when I'm likely to get both back

Marco.