Hmmm, well I tried all the various options I saw: holding every conceivable button combination, reinstalling the newest firmware, reinstalling an older firmware, formatting the player (from within my OS and the player), yelling and swearing at it, charging to full and letting it drain completely and a few other methods.
Ultimately none of the above proved a long term solution as the screen became scrambled and pixelated within a minute or two. Finally I stumbled across another forum which suggested opening up the player then putting it back together, so left with no other option I tried. Surprisingly enough it actually worked, the screen went back to normal and everything worked fine... until I turned it off. Since then it hasn't turned back on no matter what method I try. My OS doesn't recognise when it's plugged in either.
I've tried taking it apart again and inspecting any loose connection, but I can't notice anything out of place
Unfortunately mine was purchased 2nd hand, so looks as if I'm out of options unless someone has a random suggestion that may provide life again.