WORKING....!!!!
I had accidentally got a bit of solder on the side of the LED next to it.
All re-soldered with better wire and it sprung to life.
Out of interest, the last time I downloaded code to it was actually not using my laptop, it was using the Codebender app on my Chromebook, so I've inadvertently found a really nifty way to put the code on.
Thank you so much for all your support.
Me and the working gemma in mission control:
https://drive.google.com/file/d/0B-oBoD5xJkQYbFUtTy1ENkxsSVk/view?usp=sharing
If you don't mind, I will go ahead and send the dead one back as I am interested to see if you can resurrect it.
Thanks again, Becky