Here in the USA, it seems that radios do not need codes to work. Probably most USA market cars are sold with radios so the black market for OEM radios may not be so large
On an English Ford forum there is a great deal of posting of 'radio codes'
Empty out your glove compartment [dash storage container on passenger side] and inspect very closely for any numbers written on the inside.
Owners manual would be another place to look