You listen to MW/LW

JOKE!

As Ian says, make sure its plugged in at the back. If there are no obvious places where there could have been an external ariel in the past, then it may of had a windscreen ariel and the screens been replaced with a non-ariel one in the past.
Maybe retro fitting an ariel on its side inside the front or rear bumper housing could work? (seen this done on another car when the owner wanted the ariel removed but wanted to listen the radio... worked quite well) Either that or look for a Rear heated screen ariel from an Omega as you could retro fit this to your carlton. It uses the heater wires in the rear screen as an ariel, but keeps the heater functionality
