Jerry
I do not go along with long term transmission fluid. Personally my S-type Sport, 2.5 was done at 60,000 miles. As for DPF, I in my opinion do not feel DPF regenerations are that expensive. Admittedly "expensive" is a subjective issue. You seem to think a lot of your Jaguar (as I am mine) and I would not think of selling my car. It has done 66, 000 miles form new and I recently had to replace Catalytic Converter which had died due to a misfire I had, also at the same time fitted all new plugs, all new Ignition coils, new Lambda sensors and new inlet manifold gaskets. The total cost me around £1200, which I did not feel was expensive.
As for getting your money back. Yes used cars did rise in value, mainly due to certain new models not being available. Having a son in law who is a sales manager at a main agent, I am informed that the price of used cars has peaked and is now dropping again.
Surely your decision has to be based on being able to afford to buy a new car along with any desire you have to keep your X Type which plainly you think a lot of.
Good luck with the decision and Best Wishes, Regards, John