I have a 2008 XJ and I have just recently replaced the water pump. After about three hours of researching online I was able to confirm that the Ford OEM water pump part # PW448 is the OEM pump for Jaguar.
Rock auto has it for $125.00. You will find it under the Lincoln LS 3.9 engine for 2001-2005 MY. Ordered from the Ford dealer and it was delivered next day with no extra charge when you pick it up at the dealer.