Spent the morning dropping the steering rack out.
Rather pleased with myself as never tackled anything that major. Took me 1.5 hrs with nicely skinned knuckles but managed it in the end.
Bad news is that there doesn't appear to be anything wrong with it. There is no play in the steering box itself and it all seems fine, so the problem must lie elsewhere,
Maybe the Universal Joint that connects the steering column to the steering box.
I have a spare one of those, but according to the original designer one end is welded to the steering column so I will have to get an expert to tackle that.
Postscript: I replaced both the bolts (which were bent) with new high tensile bolts and nyloc nuts and it is now certain that the UV joint is worn and will need replacing.