I finally got sick of the dragging front left brake caliper thats left me with an under thickness rotor and a prematurely worn out set of left brake pads. Oh and the smell of overheated brakes after a highway cruise and noticeably higher fuel consumption (9.5L/100km instead of around 8.5L/100km) during highway cruising.

Anyway I purchased the kit and read the manual that advised removing the caliper clear of the rotor and getting and assistant to gently press the pedal, the piston should then work its way out of the bore. Tried this with a piece of wood between the piston and caliper back plate with enough clearance for the exiting piston and plenty of rags to catch anything that fell onto the ground.

Well SWMBO pushed the pedal and I could see the piston move 2-3mm then stop. She reckoned she couldn't push the pedal any further. It was getting dark and I feared that I shouldn't proceed for fear of breaking something or high pressure fluid going everywhere. I tried to manually by hand free the piston and it just feels like its well and truly stuck in there.

Should I just hook the caliper back up and apply greater force on the pedal?

Sorry for the long post.

Yep. Pedal needs pumping a few times. There will not be any deadly release of high pressure fluid, the piston will simply fall out and be suspended by the boot.
Done it this way plenty of times.
Wash out the caliper, clean rust spots off the piston, and reassemble.

Thanks Max,

I will try this. I also noticed that the bottom guide pin was heavily corroded and pitted. Even after a thorough clean of the pin and bore followed by re-greasing. The pin will not slide as smoothly as the top pin. I wonder if I can purchase individual pins.

Thanks Max,

I will try this. I also noticed that the bottom guide pin was heavily corroded and pitted. Even after a thorough clean of the pin and bore followed by re-greasing. The pin will not slide as smoothly as the top pin. I wonder if I can purchase individual pins.

Not likely. Wreckers, grab a pin, boot and bolt, or a whole complete caliper.