Also many thanks to les and ab for producing this - best one so far, I thought.
Favourite was 27dn - should have been obvious, but it took me ages to see it. Also 44a (the one I butchered!)
I struggled with 35a because I had never heard of the sportswear company, and the original Olympic competitors competed in the nude!
A minor quibble on ab's brilliant 24d (Chambers fault, not his) - inorganic chemistry includes the chemsitry of carbon dioxide and the carbonates, so not quite ALL inorganic compounds do not contain carbon.