1999 AU1 with Au111 brakes

[bruce g]

Hi Guys,
I own a AU 1 1999 xr8 manual and have used this site to upgrade my front brakes to series 3 which worked out fine.
8 months ago i stopped using the vehicle over winter last Friday i took the old girl in for a warrant and failed with the right front caliper jamming on.
I went back home pulled the caliper apart found 1 pot was seized so i replaced the caliper with one that i had pulled apart cleaned up and all parts are easy moving. Fitted back on the car bleed the brakes and you could see the brake pads moving and locking on to the rotor and not releasing. I have checked the line for kinks and the hose for squashed points but all is good and changed the brake fluid.
Also went to the extreme of changing the ABS unit thinking maybe a valve was not releasing when your foot was released. I changed brake pads thinking they may have been too big. i have to push the pistons in the caliper back in with a G clamp even with the bleed nipple released. while doing all these changes the passenger side works fine every time.
Im thinking its something easy that i have missed, can you guys please give me a new direction to try. I was thinking brake booster and master cylinder but its only 1 caliper playing up not all or fronts or backs.
Problem is when i pressurize the brakes the driver front does not release
Thanks in Advance