So basically all that could go wrong went wrong.
At least you managed to make things work.
That's what I do and why people ask.
Would have been easier to just get a new door. That sounds like it was a true PitA.
I think my father in-law saw the door the neighbour had changed and thought he could make good use of it considering a new one in that material would cost about £90. I think by the end though even he wished he hadn't asked as (as XT said) everything that could have been a problem, was a problem.
It looked sweet once finished though which is the important thing.
It depends on the door.
Had a new door been solid oak for instance, it would have been no fun at all.