Chris,
Many thanks indeed for the comprehensive, idiot-proof, answer - music to my ears!
Norman, I can't say if you're right or wrong having gone for just the button itself (not illuminated - looked a bit neon to me so kept it basic), but I'm sure you're right. The information on all the sites where the button is mentioned is limited to day the least (mind you, it is just a button I suppose).
As for that functionality, am I right in saying that it would probably be of most interest to those with Q-R steering wheels (i.e. those without steering locks)? I can just see myself starting up and belting off having forgotten to turn the key to allow the wheel to turn
Thanks again,
Adam