Forget attorneys. Forget begging, pleading, and wailing. You will be time and money ahead if you simply give up now. And get on with fixing your XF.
Jaguar USA does NOT stand behind out-of-warranty vehicle defects. Period. Neither does Mercedes or BMW. Not so sure about Audi. Lexus will. The others will not. Of course, Honda would fix your defective car, as would Toyota. Quite likely Hyundai. Makes no difference.
So. Get on with it.
If you have no money, you are completely dead in the water. Sell it for parts value, likely less than $10,000, and take the bus to a buy here-pay here car lot.
If you can scrape up $10,000 to $20,000, buy a salvage 2010 XF with a good engine and arrange the swap. You will pay $10,000 for the XF and you will pay $3,500-$7,000 for the swap at a decent third-party independent shop. If you can store the bits, you can slowly sell XF parts off both cars and, over time, recover a chunk of your costs. It will be a long slog, and you must be able to store the damaged car and parts while pulling bits for sale.
All in all, it is a rotten deal. But. That is the way it is ..