Probably my final word on this. Over Christmas I've allowed the battery to slowly lose charge. I've tested response each day. Today at 3 degrees C the immobiliser was sluggish. I put the multimeter on the battery and it's showing 12.18volts. Its now back on charge. From this I'm deducing that 12volts is the point at which things might get awkward. But I carry a 12v booster pack when we're touring so I'm reasonably confident, now I understand what's going on.
DaveW '05 Red Roadster S1 '16 Yellow (Not the only) Narrow AR GDI Plus 4
