This is now on the way to being fixed...
I identified a potential faulty disk and confirmed this with the manufactures disk checking tool
After adding a new drive the Storage Space came back online and I am now removing the old drive by 'preparing it for removal'. In this process all the data is copied off to the other disks (and in my case to the one i have just added which is obviously empty).
The problem for me was the Bad Blocks were not really being reported in windows or Smart as a problem or an unhealthy disk....so it looked okay but Windows knew it was faulty and could not really be written too. Which then took the Storage Space down.
You do need a lot more than consumer knowledge for Storage Spaces troubleshooting but they do offer a degree of resilience to users data.
hope this helps someone.
Basically look at NTFS logs and disk events in event viewer, work out which drive or drives is the problem and then look to replace them
--All confirmed fixed now