Welcome to the world of old Fords.

When I bought mine several months ago it had a similar misfire and it was indeed down to the spark plugs, the engine light is probably due to lambda sensors faulty and as for knocking and juddering then the clutch/flywheel would be a good guess

Lift the rear seat and check for rust on the bottom of the wheel arches, if sound and it does need a new clutch it might be worth doing, if its rotten and needs a new clutch then scrap it.

Either buy or borrow a code reader and see what error codes its showing, I would recommend buying one as its the most useful tool now on modern cars.

Good luck, you are going to need it!!