I would also check the disc ( rotor for USA !) condition and the flexible pipes. If you are refurbishing the callipers you might as well go over the whole system for other signs of ageing issues. Your symptoms certainly sound like sticking pistons/calliper/pads.
Low mileage Morgans can easily deteriorate due to lack of use. Rubber parts harden, perish, electrical connectors get dirty, corrode. Fuel lines deteriorate, ethanol might cause problems.
