Hi Steve, as Mark has said above, it really does come down to a personal "feel" for all things considered. The 5 litre engine is VERY robust and reliable, but a gap of 3 years in the servicing (at least twice now, would make me think long and hard. Ideally, the oil should be changed annually, irrespective of the mileage between service intervals, but nothing much else in the service regime is such an issue.
My mind would think that if the previous owner(s) had skimped on getting the servicing completed - which is not at all a cheap item at a main dealer (circa £600 each visit), what else has been skimped on, so look extremely carefully at all other aspects of the vehicle before committing hard cash into the deal.
With the car at coming on 10 years old, the tyres could be needing changed - 5 years is about it on these cars, irrespective of the tread remaining. The tyres should also be premium branded such as Dunlop Sport Maxx in J, for Jaguar, specification. Check the tyres carefully and if they are mismatched, or not premium, have a rethink. Also check the tyre dates on the sidewall's - refer to the Kwik Fit website for information on that if you are not sure.
Also at 10 years old, the battery could well be due for replacing, again a 5 year interval between battery replacement is a good proactive / preventative maintenance option. Uncover the battery - it's in the boot behind a trim panel depending on coupe or convertible - and if it is still an original Jaguar stickered battery, once again think about the skimping that may have taken place.
These cars have large / expensive brake discs and callipers and with missed servicing regime, the pads could well be seized in the callipers and the discs scored or warped - check on the test drive for any braking issues such as vibration or long pedal.
Often, low mileage cars can be more trouble than a well maintained and cherished high miler - such as Mark has. If you do go ahead with the purchase, I hope you have years of trouble free motoring. They are fantastic machines with Supercar performance at Mondeo money.
N6 JMX