Michael,
I would add to Davy’s info: A leaking water pump – just the slightest drip – is often responsible for a sticking clutch because the drip falls directly onto the clutch area and can lead to formation of rust on the surfaces of flywheel and/or thrust plate.
Davy’s suggested method of freeing it should work – but remember to depress the clutch pedal when attempting to start it in gear. If it does not fee off easily and the car lurches forward, immediately cut the ignition as well as applying the brakes.
You might also be able to try with the ignition off thus reducing the chance of it firing but not freeing.
B…………