Whilst I was disappointed with GBS for pushing old stock my way, I don't want to halt the build whilst I argue with them over a replacement.
Positioning the lower front lip of the base of the nose along the chassis rail shows that the cut-outs for the upper wishbone (either side) are not deep enough to allow the nose to sit properly on the upper mounting brackets. I approximated the amount of clearance I needed and drew up a template. After cutting and shaping the dash yesterday, removing some of the nose to extend the cut-outs for the upper wishbones didn't take long.
Holding the weight of the nose on my trolley jack I then marked and drilled the lower mounting points along the chassis rail and installed some rivnuts. I used low profile M6 bolts and some large penny washers to finish the fix. Then I made sure that both sides were level before drilling the mounting holes for the upper mounting brackets.
The above sounds quite straight forward but it has taken all afternoon. I still need to add IVA trim around the nose edge and also the upper wishbone chassis brackets as they are now exposed - but that's for another day.