How To Fix A Seized Jaguar Engine?

It has to be taken apart and all parts inspected. Almost certainly there will be work to be done to the pistons/cylinders. There could also be bent rods and damaged bearings.

Forget repairing it replace it unless you know what you are doing and are doing it yourself the labor alone you would have to do a hit for someone to pay for it

Go to a salvage yard and buy a new, one and put it in it.  Chances are it will cost you more money to take apart and inspect  /replace broken/ seized parts then it would just to buy a used one.