[undecided]

Hi Bruggz sorry to hear your overheating problem has reached its pinnacle.Please be aware of 2 things.
1 water and piston rings do not like each other, blown head gaskets can lead to broken rings.
2 on a high mileage motor if you remove the head and have it serviced you can put it back together only to find you have blow by. that is the rings cannot hold the compression.
I mention this cause in the longer term you may find a complete engine rebuild a better option.
I suspect that this problem had already begun prior to you purchasing the XJ. It is rare head gaskets fail in one foul swoop. It is normally a slow process that is not picked up until it becomes a larger problem.