[CharlesJones]

I've heard it's common for them to fail, although I would have thought it would be more likely to break than bend. Perhaps it has cracked or bent, and so not is not getting sufficient range of movement to release the clutch? It's a pity the inspection hole isn't a little bigger so you can see more of what's going on in there - perhaps it's worth it to keep trying to peer in with mirrors or whatever to see if you can see any such problem.

Just another thought - would it be possible for the clutch plate to have become fused to the flywheel somehow? I had that happen on my old Morris Minor after a few months of storage, and I had to put the car on axil stands, start the motor in first, and then dab the breaks whilst the wheels were going round, which freed it off with a loud pop! I doubt this is your problem, but it's just a thought.