I have a 2003 MX5 and recently had to recharge the battery. The radio now requires a code, the display shows the word "code". I have not yet entered anything - does anyone know how I go about fixing this?

When I contacted Mazda they used my car registration to look up the code but could not find it - this leads me to think that perhaps it is a simple 4 digit code.

Many thanks

Adele