I have found the guys at Kent Jaguar Centre really helpful and knowledgeable. Labour rates are far better than Main Dealer and you're paying for widely experienced Jaguar mechanics, not £100+ per hour for the latest apprentice mauling your favourite pussy cat.
Location is Hillside Farm, Rushmore Hill, Knockholt, Near Sevenoaks, TN14 7NL. Phone number 01595 533312. They are within 2 miles of M25 Junction 4, so very easy to find (with the help of Multimap).
They carry good spares at reasonable prices (including some good quality refurbished items and reclaimed parts) and have knowledge and experience with all Jaguars and have done comprehensive suspension overhaul on my Series III V12 and will soon be let loose on my XJ8 Sovereign.
If you're in the area, then give them a call.
Alan C