Hi Gary,
I also have a 2017 XF.
We may not have the same satnav system (mine doesn't use DVDs - it's a download to PC, copy to USB and load from the USB to the car).
My subscription to Here (the map provider) via Jaguar cost £129, but that's for three years of multiple downloads covering UK, all of Europe and, bizarrely, Russia. The maps are updated regularly (at least monthly), but I probably get them once every three months or so.
Hope that's of some help.
Cheers,
Jon