There are differences between Jaguar's Select Edition and aftermarket warrantys that you should check before you decide. Some aftermarket plans include a lot more items than Jaguars plan. Some aftermaket plans allow the use of used parts from a recycler(junkyard). Jaguar's plan does not include bushings and trim items. Only you can make the decision you are comfortable with.
I put in a used( rebuilt) trans from an aftermarket company yesterday in a 99 and it has a very harsh engagement. I would not be happy eith it.
I would not buy a Jaguar without some king of warranty. Repairs can be very expensive. Grumpy has been very happy with his company, perhaps he will answer also.