How to unlock my radio/CD player?

Fiat Doblo 2004 model. I had to get my code when the battery was changed. Unfortunately, in the meantime, my wonderful son had punched in random numbers. Apparently you only have a limited number of attempts before you are l;ocked out and even the correct code will not work. My local Fiat dealer has told me they can do it but they have to send it away and it will cost £200. I can buy a new stereo for less! Any suggestions how I can solve this. I have tried disconnecting the battery but this doesn't help. All that comes up is 'wait' and this has been the casre for a few months now.