I think you're right Rory. That looks like a home grown fix for a busted crank on the 1.6.
A machine shop might be able to fix it, but probably not with it on the car. So, you're either replacing the crank, or repairing the crank... either way, it's got to come out of the motor.
Or you could just try to weld it up some more like the previous owner did and drive it like that until the crank pulley tears off, then fix whatever else breaks then.