Stamping my carbon footprint!
I just did some checking around and according to this Jaguar X-Type site, bank 2 should be on the left as you stand from the flywheel end of the engine so I think it should be at the front http://www.bluejag.co.uk/X-Type bank1-sensor2.phpWent to Ford yesterday, they didn't know which was Bank 2! Their system said it was the same sensor front and rear too. Wanted me to pay £86 diagnostic fee to "unplug one and see what codes it chucks up".
What sort of price are you looking for? Couldn't hurt to replace the front one, which looks to be a lot easier than the rear one.