Regarding your first comment... Changing the battery on the XF is slightly complicated. In true idiosyncratic Jaguar style, the car tends to go crazy just before the battery conks. If not for google... I would have had a stroke! Even though you can start the car (so you don't suspect the battery) the dash starts throwing up all sorts of faults; including "ABS unavailable", "DSC fault", "Gearbox failure" etc.
When actually changing the battery, there is a bit of a process to properly earth it because there is a sensor array attached to the battery (which is in the boot). Then you have to either plug in a terminal and save all the settings of the car (some of which are system related) before you yank out the battery OR piggyback off another battery while you swap out the old one. There is also a bit of skill involved in safety removing and reconnecting the above mentioned sensor array.
All in all... not something that can be done by your average battery joint. The battery also has a relatively high 100 amp-hour rating, so its not easy to find.
On the second comment... it was this aspect that really grabbed my attention as well. When he first told me he offers a jag as a replacement vehicle, I thought it was just a marketing gimmick and he would never actually follow through. However, both times I have had to leave the car at his workshop (even for a couple of hours) he has offered me an x-type as a replacement.