Buy from a reputable Jaguar part specialist and try to find "OEM" labelled parts. These are from the original manufacturer that supplied Jaguar, and tend to be much cheaper. In addition, on this forum there are details about which Ford parts fit. They fit because the suspension is essentially the same as the Lincoln LS and parts cost far less for these. Jaguar under Ford had a bit of a reputation for stiffing Jaguar customers on parts. It's now a lot better under Tata Motors, like the rear lower arms are now less than half what Ford were charging.

There wont be any difference in ride quality BTW. The best way of doing this is to downsize the wheels so you get fatter tyres.