Qman

You dont need to take the box out. If you slacken the bell housing bolts and turn the engine the misalignment of the primary shaft should free it. I used this method on an Etype many years ago and saved hours of work. And on a Herald you can reach All of the bolts from the top

You will need to take the manifold off. If there is any stud protruding it might come out with mole grips but I would suspect you will have to heat the maifold where the stud is with oxy torch to remove it. If no stud is protruding then it will have to be drilled and removed with an easyout. Heat will most probably still be needed. Or you can drill the stud out and re tap the thread. This will require a fair degree of accuracy. Mine came out with heat.

Have you worked on the front calipers? I once had a low pedel caused by the seals in the calipers twisting and pulling the pistons back as they twisted back to normal. If this is the case you would have to remove the pads (1 side at a time) and work the pistons until they settle to a stable state.