This is too much like coincidence to be anything other than 100% my fault!
Just went out to flick the switch on my Alpine power module from hi to low gain to stop speaker distortion.
Dd it and reassembled, then car would not start. Won't even turn over. Alarm pips and that's it, but A/C etc all working.
Might this be fixable by a fault code reset via the OBD port? Or maybe more sinister? AA on way...
D'OH!!!!!!!!,