Ok so I got a reply from Kobo, asking me to perform a factory reset using a different method than those above (hold light button, press reset button, release light button when LED turns white). I did this, and thought nothing had happened. Went to try again, just in case, and as I pressed the light button, it came on! And stuff got weird...
Again, apologies if the picture doesn't work correctly!
The light bar appeared, but is not responsive. I can turn the light on and off, although it does not always work.
I'm surmising from this that the issue is indeed the screen?
Thanks.