Hi David,
I cannot thank you enough for your patience, help and advice with my issue.
Finally, after following your explicit instructions, especially the last one of downloading the firmware, I am now back up and running and able to read again.
I followed all your instructions and, believe it or not, I put all the software image/firmware on the original [Sandisc] SD card that it came with and it is working fine. As I had already purchased a new 4gb SD card anyway, I just decided to copy the lot on to it as well so that I now have a backup should the same thing happen again. I can only imagine that for some reason, the original SD card somehow became corrupt.
Before I found your site, I contacted Kobo Customer Services and explained my situation. Sadly, they were as helpful as a chocolate teapot and could only offer a slight discount on a new Kobo ereader. Thankfully, I used the trusty internet and found your site which has proven to be a godsend.
Thank you once again and keep up the good work.
Kind Regards,
TrevTheBev