Great thanks - didn't try play due to this comment in the documentation
"MQTT program must be downloaded to use!"
Have tried it and play seems to work ok. I seem to have to reset the device though to download a new version of the code, but the good news at that after reset it goes back ok into the cloud connect mode ready to receive a new version.
I have found that I can do this - programatically using
import machine
machine.reset()
Just wondering if there is a way to avoid having to do this step when operating in play mode.