Estate radio Ariel connections

Just got my 56 plate Skoda estate but found I could not get good radio reception. Looking at other posts it seemed to indicate the antenna base and this seems to be confirmed by an ANT off in the menu. Looking at replacing the unit I expected to find just one coax type connections, what I have found is that the coax from the harness is not connected to the base but coming out of the base are three wires, two black and a red, which just seem to disappear under the head lining with no disconnection plugs. Any suggestions about what I have and how to repair it would be appreciated. Thanks