Radio code required for Vauxhall Astra?

Following maintenance to repair a broken altenator the radio has gone into safe mode. Can anyone help by supplying the radio code. The model is VDO CDR 500e and the serial number is GM050011129035. Vauxhall want £25 to supply these details which i think is disgraceful when i can clearly prove ownership of the vehicle.( but unfortunately was not given the code when i bought the car). I would really appreciate any help out there, cheers