JBMd,
Common problem when you have too many sitting cars. My 1975 TR6 is a perfect example. What has worked for me every time so far even after several years sitting. With the wheels on the ground and the car in neutral get the engine running and warmed up. With engine off put the car in first gear and use the starter to get the car started and moving up to a good idle speed, making sure there is plenty of clear road in front of you. Next push the clutch in and then do a major hurkey jurkey on and off the throttle and the clutch will almost inevitably let loose. If it does not happen in first gear dry shift into second and try again and so on. Takes some guts but as they say no guts no glory. On a hill you can have the engine running in neutral and let it roll up to 5-6 mph and dry shift into first depress the clutch then do the hurkey jerkey on the throttle. This concept puts way more torque on the clutch plates than applying the brakes up on jack stands. give it a try before you buckle and start taking things apart.
David