Acting on information supplied on here.... I went for a Telephone Pick-Up Coil plugged into my dictaphone. Works a treat. Should plug into the same socket as your lapel mike on your camcorder.
Again, available from Maplin at £4.99
Telephone Pick-Up Coil : Electret Condenser Mics : Maplin
Just a bit of tape to hold it in place on the outside of my DC - picks up ATC and intercom very clearly.
HTH
DD