peugeot 306 car radio?

last christmas my car battery died and my stereo went with it...I put in what i thought was the code - It was the wrong one and wouldn't let me guess again. Ever since then I've tried disconnecting the car battery, drove around for 2 hours or more with the radio on, and someone said holding down the 'on' button with number 6...But nothing has worked. I dont wanna fork out a load at the garage for something that I might be able to do, so if anyone has any suggestions they'd be greatly appreciated....It's a peugeout 306 Meridian T reg. Cheers