Matt,
My 62 plate XF S 3.0D has been Jaguar serviced since new. It has done 82k and its next service will be, according to the book, the 106k (12mths or 16k (which ever is the sooner)) during which they will change the timing belt.
I have a service plan with Jaguar which spreads the cost over the year as this service will be around £1500 (main dealer prices) due to the timing belt change etc.
Hope this helps.
Clive Hunt