On my 2013 XF sportbrake the problem was faulty front bumper wiring loom (front offside parking sensor connection corroded) replaced for less than £200 by Jaguar dealer. On the XF the parking sensors and camera work as a complete system so a fault in any part can shut down all of it, eg a faulty front parking sensor can stop the rear camera working as well as the parking warnings.
If it was me I would be trying a good auto-electrician as they should be able to repair the wiring loom or even replace it with a used one for a fraction of that price. I would only expect that sort of cost for replacement of the entire wiring for the car. I know it is apples and oranges but I had the entire front wiring loom replaced on a Peugeot 208 by main dealer for £1200 4 years ago.
Good luck