Lots of people do not replace the fuel filter for the entire life of their car. You should replace it obviously, but I've only seen fuel filters cause a car not to start on very old metal fuel tank cars with CIS fuel distribution systems. Jaguar S-types have a history of crank shaft position sensor failure. With almost any hand held scanner that will show you the data stream, you can observe RPM speed on the scanner hooked to your car while you are cranking the engine and trying to start it. If the scanner reads 0 RPM while the engine is cranking, then you have a bad crank sensor. This part is available at the jag dealer for around 30 bucks. The sensor is located behind the passenger front tire. remove the plastic in the wheel well and there it is. Honestly though, that's just the most typical S-Type No-start issue. There are a great many causes for no starts in all cars. That jag also has a very sensitive PCM (engine control module). That is the computer that controls the operation of the engine. If you have jump started the car improperly for example, it could be damaged.
I can only only advocate chemicals that I have experience with over a long period of time. Lubro Moly is the only brand of fuel system treatment that I've seen run in vehicles for periods of time longer than 100,000 miles. It is the chemical that we use on our personal vehicles as well as on customer cars. I can, however, say that I have never heard anyone complain about Lucas products.