Finally, I hope, sorted the rear brake on the Corsa. The rear caliper was sticking a bit so I cleaned up bit of corrosion on the caliper bore closest to the pad and re greased the piston and seals. Also discovered the rear M/C was a 15.8 mm (as I recall, just less than 16mm, or 5/8 " bore). Replaced with an 11mm one. Using the Forum to remind me best way to bleed the rear brake system as it had been a few years since I had done it. I bled the M/C first, then attached the brake line and caliper. The trick is hold the caliper up high and use rapid short gentle strokes ( I'm talking about the brake pedal here, you can use any stroke you want for other things) to bleed the line and caliper. Sure feels more compliant now but need it warm up a bit before I can road test it. Snow is gone but north wind coming across 400 km of still frozen lake (ice is 1 meter thick) is keeping it cool.