OK success.

I'm pleased, now I have a working codebase that I can begin to refine!

It was not receiving because in the setup code for RX I left out the oh so important enabling of the CE pin !

 

I think this thread is done really given that it was initially about the STM32 clock. I will start a new thread if I have any questions ort problems with my NRF2401 work.

Thanks to @MrChips for his help - I will likely be picking your brains again soon...