Bad news, it seems....
1: I downloaded Peppermint3 mainly because I already had v2 and wanted to see the improvements.
This could not see the drive, but that wasn't a surprise, for it is a Ubuntu variant which I had already tried.
2: No pont sending a Disk Management screenshot because it only shows drives it can see - "Absence of evidence isn't evidence of absence"!
After trying Peppermint3, I rebooted and it went through the process of seemingly hanging for about an hour, displaying the standard pre-desktop screen [ not the BSOD]
The usual "There is an error - I need to check drive G:" etc came up and off it went, displaying a torturously slow segment-by-segment analysis of duff elements. This continued for 2 days until complete. It was obviously 'seeing' data because it was referring to recognisable file names when re-indexing.
When Win 7 finally settled to a working desktop, it was possible to 'see' the drive using an Explorer window and it stated the drive 'needed formatting before use'.
I then fired up the command line option as Administrator and ran CHKDSK G: /F /R, hoping this would be the most extreme repair option available to me would work.
Two days later, and the same again [ ....drive 'needed formatting before use'., etc.]
Checking drive properties revealed nothing - literally!
Using Disk Management caused it to disappear again.
I fear this data is now lost and think it might be time to drill a hole, unless anyone knows and tricks to repair from command-line services?
Mny thanks for all your help so far.