Fix for this was as follows:
It was the collars at the end of the seat front height adjustment rail onto which the seat clips. They were creaking like a brides bed.
Squirting with lube was ineffective. So remove whole assembly and removed rail. Soak Inox lube into ends and reassembled. Quiet as now.
Hope this is not a regular maintenance job as its fiddly getting it apart, back together and aligned again.
So if you have an annoying creak try this fix.
