BMW E46 Aerial Connection

[s.deeming]

I recently bought a BMW 3 series coupe which had a cassette player so I wanted to upgrade it to a CD player. Probably a little foolishly I bought one on ebay from the States but have encountered a problem with the aerial connection. The player has connection for a Farka adaptor but the original player was ISO. I think the BMW harness is pre-wired for the Farka connection but I think I need to change the connection at the antenna from ISO to Farka.

Does anybody know how (or if) I can do this? I'm not sure but I think that the antenna is in the rear screen.

Any help would be much appreciated.

Steve