I have watched the price of classic and semi classic cars for many years. This is a model of car that is inevitably going to become a classic of the future (if not sooner). In my opinion after the XK type models and S-Type models Jaguar have not made particularly many (I am not saying none) cars that reflect being a Jaguar by design.
Personally I believe this model of car is worth what the seller is prepared to take for it, versus, what you as the buyer is prepared to pay for it. Price, in my opinion, is not the only and utmost regard. I believe a provable service and maintenance history is important and part of a value, as is mileage and condition. The important factors in condition are, including mechanically, bodily and internally. You seem to suggest that all of these factors are sitting well with you in respect of this car.
If you consider it a price you are prepared to pay then the best you can do, if satisfied that the car is all good and what you want, is make an offer for the car. You may be lucky to negotiate the price down. On the other hand you may not and have to make a decision (which only you can do) on whether or not you will pay the asking price.
You have not said if you are buying from a dealer or if you are buying from a private source. No doubt you are well aware of the different legalities from both, so bear this in mind when making a decision. Be aware of what/if a dealer is offering a warranty, as to what is covered by that warranty and the conditions attached to it.
Good luck with any negotiations / decisions. Best Wishes and Regards, John.