Thanks for your comments.
Having a poke around this morning, it may be that the paint/lacquer is the issue. Both cracks are in the inside of a curve where paint might gather/pool when being sprayed (and therefore be thicker than the norm). I have given the cross piece a pretty firm pull and there is no sign of movement. I have also tapped it and the sound is quite normal.
I have the benefit of a factory warranty, and am reasonably confident of the vehicle's provenance. All the services have been done by the factory, which proves nothing, but was part of the appeal for me.
It will be interesting to get the factory feedback on this. Stay safe Tim
