Kevin.
I just want to thank you once again for your superb help - I burnt the IMG file you sent me using the disk imager software and it has solved the problem and all is now well again

- thank you SO much.
I honestly thought I had an out-of-warranty brick, phew!
I do wish Kobo would implement a safety feature or proper factory reset option somewhere though, to avoid all this heartache when updating firmware - I won't be running any more updates in the future for sure.
Thank you once again, and to these excellent forums that gave me hope
Tim.