Well if its a VX radio, Theres probably only one option.... A trip to Vauxhall with the car and radio. Vauxhall pair all their electrical items to the car's CPU. You cannot even whip the stereo from one Vx and put it in another. If a part is removed (including an airbag controller for example) it has to be unpaired before removal. If the radio you are talking about is newer than say an 02 plate, you are gonna struggle. You could ask on a Corsa website.
argh god damn it! there just making the market sour now with the stupid rubbish there doing to new cars! how long are everyone going to put up with this!
Right done a little digging on my vectra forum and safe mode APPEARS to be a mode were the radio code is required. If it is the original radio from the car, the owner should have a card with it on. If not he/she may be able to pay vauxhall £25 quid for a new card. (No Promises mind)
Google Tech2 aswell. That is a tool Vx use to program these things. Some garages have started offering this service though they are few and far between. I think there may be one in Crewe.
Pressing the AS button when switching on should let you put the code in. Disconnect from battery for 15 minutes to reset if you go over the 10 goes. These are really easy to get the code from if you have the software. There are a number of forums that will do it from the serial, but it has to be a certain type of brand.