Vauxhall Zafira Radio /CD won't work/panel stays illuminated/outside temp display stays on

Delco Electonics CDR500 stereo - won't turn on, the backlit panel is permanently illuminated, also the in car information display (time/outside temperature) is also permanently on - but not the date. Turning ignition on/off makes no difference. Started last night, worried that it may eventually flatten the car battery now it's getting cold. Suspect it may be a fuse blown/short circuit or something similar - any ideas anyone?

Thanks