Mk3 radio code

[Gipson]

Hey mk3 owners
I have a mk1 with a mk3 standard radio fitted into it, today the battery terminal was knocked off and now I need to decode the radio for it to work, as I don't have the code or any of the details from the car it was originally in, is there any mastercode or other way i can get the radio back on?
Thanks in advance
Dan