Vauxhall Corsa Stereo Problems?

[Kyle]

Hi I have a '94 corsa GLS. I have an aftermarket HU/Stereo fitted but when i turn the engine off, the whole ignition and stereo goes off even when the ignition is still switched on the first notch. The first notch is accessories and should turn the whole ignition on when it is turned to the first. However, in order to get my stereo to turn on, i have to turn it to notch 2 and when i switch the ignition off, the stereo goes off and i have to switch the ignition off then back to number two again. I know this is not right because my cousin and dad both have corsas and their ignition work on the first notch and when they turn the ignition off, it doesn't go off until they remove the key. However mine goes off right away. Please help. Thanks