A little update to this. I fitted the aux adapter, supplied by Fruity Car Cables, the other day. The connection to the back of the stereo was taken with another block connector although the three spaces required for the AUX were available. Rory from Fruity was very kind to provide an additional wiring loom so I could connect the wires directly to the existing block.
Drilled the hole to the panel below the heating dials and all works really well.
Drilled the hole to the panel below the heating dials and all works really well.