Not sure what part of Norfolk you are in and although technically in Cambridgeshire, there is Jagutek in Ely :
http://jagutek.co.uk/
Not used them myself but have heard good reports.
I'm not 100% certain on the later cars (mine is a 1999 S Type 3.0 V6 SE) but it seems most of the petrol AJ--V- engines used chain drives for the camshafts, i believe the 2.0 Ecoboost uses a timing belt immersed in oil surprisingly - unsurprisingly regular oil and filter changes are essential to preserve longevity! I may be wrong on that, Jaguar may have altered it somewhat but i know a lot of the Ecoboost engines use that arrangement.
With the autoboxes, most were "sealed for life" although the WSM recommends changing the fluid at 80k miles if used in "extreme conditions". What those extreme conditions are, it doesnt really specify. Again, this may have changed on later models so it's worth getting to know exactly what engine and transmission you have and working the exact requirements out from there.