OK - just following this up with extra info.
Previously, I was using radios without the cap.
Once a 47 uf cap was added, I didn't need the extra power supplies (the USB power was enough to the Uno clones).
Thinking about this now, It wasn't the uno boards, it must have been noise/weak power on my laptop USB.
Also, I wasted a lot of time on a bad rf24L01 board ( I think I bust it a while ago by supplying 5v ).
So, the moral of the story?
- If you get a message saying "radio bad" - try another rf24l01
- ALWAYS add a capacitor to every rf2401 board