Thanks Cobrin. I didn't look at the piston, seemed easy enough to move, I have CRC Brake caliper grease but didn't use it because the original grease looked fine. Now installed the brakes and pedal work fine.
I made a few notes for next time, any improvements or corrections appreciated:
DIY RENEW MC BRAKE PADS AND ROTORS.
Apply the handbrake and remove the T50 disc securing screw.
Release the handrake.
With 10" adjustable spanner wind the handbrake spring back and remove the cable nipple from the lever.
Remove the cable with long nose pliers by squeezing the tabs on the plastic retaining ring and pulling on the cable (easier said than done, and the tabs are easily trashed, being very flimsy).
Remove the slide pin retaining bolt with a 13mm spanner.
Use a 15mm spanner to prevent the slide pin turning.
Remove the caliper and support it somewhere out of the way. Remove the pads.
Use an 18" bar and 15mm socket to loosen the caliper mounting bracket bolts and then remove.
Remove the disc.
Temporarily install the mounting bracket and caliper with lightly tightened bolts.
Make provision for dealing with the brake fluid as discussed below.
Wind the piston back to the stop with a clockwise rewind tool and close the bleed screw. The plate on my rewind tool needed shortening to 75mm to fit inside the caliper.
Remove the caliper and support it out of the way by resting it somewhere. Remove the caliper mounting bracket.
Instal the disc.
Instal the mounting bracket, pads and caliper, having cleaned everything and lubed the guide pins ONLY.
NOTES
I fiound it easier to wind back the piston when it was installed in its usual place, ie bolted to the caliper bracket.
Brake fluid:
The concern may be that particles might enter the
ABS system.
A few ways to do this:
a) Clamp the brake hose closed and open the bleed screw with a tube to a container.
b) Apply pressure with a pressure bleeding device and open the bleed screw with a tube to a container. Caution: Do not exceed 14 psi, as per Ford manual.
c) Just loosen the bleed screw to a tube and container.
I don't like clamping the hose for three reasons: the hose is stressed, debris could delaminate fron the inside and if the bleed screw is open the fluid isn't going very far up the brake line. I use a pressure system.