andy i think you could be spot on .we have lifted the carpet etc and there are 2boxes one- from part no- is the remote keyless entry module the other has a merc part no but means nothing to the parts dept(Q350 010 21).it has approx 24 wires in 2 multiplugs all different colours.any idea how it was wired to immobilize.would it physically switch 3 or more cicuits or would it do it through the engine pcm.there is a siren in the engine bay and 2 wires to the front panel possibly for bonnet switch .the rest of the wires seem to go forward and back but remain in the cabin and difficult to trace behind the dash.any clues to my nextmove.thanks in advance regards paul