Well further to this, I've just compared the back faces of the 240 & 260 steering wheels, & they look identical.
From looking at the 240 wheel pic one of you posted, the bit I'm missing is whatever the little black wire attaches to on the front face - on the 240 wheel I bought there's just a hole, whereas there must be meant to be a little captive nut, to screw into, maybe with an insulation collar around it? Can someone please advise?
Can you post a picture of your wheel centre. From what I've seen in your other thread, it looks like you might be missing the upper ring. See exploded diagram below. From memory, the upper ring had a threaded punch hole that the screw screws into, and the ring directly below it has a cut out for clearance.