Ok, after much berating of my brother and a bit of thought (shocking I know (IMG:
style_emoticons/default/biggrin.gif)) I've fixed the problem.
The epiphany came when I remembered that after modchipping the box I could not see anything on screen and this is because I was using the advanced AV lead. I read that you needed to use the standard lead. I thought I'd give the same thing a shot here and lo and behold, screen is back to normal.
Switched back to the advanced lead, still no go, so I popped the standard one in and booted into XBMC and worked out the keypresses needed to get into the settings, this would allow me to do this "blind" when using the advanced lead.
I thought I'd detail the keypresses as it might help others if they encounter a similar issue and don't have a standard video lead to hand.
The key presses were as follows (once XMBC is booted):
Press D-Pad Up 1 time
(Gets you to the "Settings" option) -> Press A
(selects "Settings" option)Press D-Pad Down 1 time -> Press D-Pad Right 2 times
(puts you over the "System" setting) -> Press A
(Selects "System" option)Press D-Pad Down 6 times
(puts you over the "Video Hardware" settings) -> Press D-Pad Right 1 time
(puts you on the "Aspect Ratio option) -> Press D-Pad Down 1 time
(puts you over the enabled 480p option) -> Press A
(disables the 480p option) -> Press B
(takes you back to the main settings configuration window - I did this to ensure the option was saved)Press Right Thumstick 1 time
(To display quick menu) ->Press D-Pad Right 2 times
(puts you over the Restart option) -> Press A
(selects restart option)After doing the above the box rebooted and displayed things correctly.