gareth, if you do not have a code, you may want to try [http://www.radio-code.co.uk/vauxhall-radio-codes.html|this site.] If you do have a code try this:"
Entering code into stereo:
Turn Off Stereo
Switch On Ignition (No Need To Start Engine)
Press & Hold Preset " AS " and
Switch Radio On - Display Shows
" SAFE " And Then Shows " 10 - - - - "
Press preset " 1 " repeatedly for 1st Digit
Press preset " 2 " repeatedly for 2nd Digit
Press preset " 3 " repeatedly for 3rd Digit
Press preset " 4 " repeatedly for 4th Digit
If the correct code number is now shown
Press & Hold Preset " AS " Until the Unit Beeps
INsP message:-
Ignition Off
Hold Trip Reset In (keep held in)
Press brake pedal (and keep pressed)
Turn on Ignition
Still Hold Trip Reset and brake pedal for approx 10 seconds, the INSP should change.
release brake and trip reset.
switch off ignition
switch on ignition and check. " hope this helps, good luck.