Success - I connected the card into the Mobius and connected it the PC. A message was returned saying 'there's a problem with this drive, scan to fix or continue', I continued. The mobius connected to the PC and I could see the drive. I then did the following.
1. Formatted the card using Msetup (mobius app/tools).
2. Disconnected and reconnected and the card could be seen by the PC.
3. Made a short test film.
4. Re-connected the Mobius and checked I could play the film with success.
All good - after further reading of the Mobius manual, it does say to use only really good format apps but preferably the one in Msetup and that poor SD cards and USB cables might not work.
My conclusion here is based on the manual and the forum feedback is to connect to the PC through the Mobius camera using the USB supplied and use Msetup to format the card.
Thanks for the help,