Hi an update. I located an airbag front crash sensor above the fan on the radiator at the front of the engine compartment. I noted the part numbers as 5wk43647, 51751186 which when I googled confirmed as same on a parts for sale site for £39, some others listed as £20 but not an exact match. However the wire loom splits at this sensor and continues through a hole in the bodywork to the void on the front side of the radiator and behind upper grill. This leaves the question whether another similar sensor exists there that may also need to be replaced. I have ordered one and will fit and re-test system with multiecuscan.net software on laptop.