Stereo unlocking help please...

[womble]

Wonder if anyone knows how to fix this.....Yesterday one of my battery leads came loose resulting in me not being able to start the car for over an hour until the AA turned up and found what it was. I did check that it hadn't come off and thought it was down to either a flat battery or at the sugestion of the AA operator was something to do with a mobile phone mast as the car had driven perfectly to my destination and had locked up fine when I left it. The problem I have now is that on my stereo which is a standard Toyota single din cassette (so much for the well speced UK cars eh !!) there is now a small illuminated picture of a key and "HELP" on the display. Anyone know how to get round this as I've got an hours motorway drive to do a little later and the thought of it without music does not appeal !.