Welcome to the club, Rob.
I have had my s type [2007 2.7D] for seven years. Like you, I wanted an s type for many years but I was hindered by a shortage of cash, then buying a house, and then luckily having company cars for 29 years. A great car to drive.
A little advice was given to me, and I will pass it on to you, as it works for me.
Always use premium fuel which is good for the engine. I also use an additive, Millers Diesel Eco plus every fill up, which keeps the Diesel Particulate Filter and the EGR valves clean.
I am told by an AA engineer that the 2.7 diesel would like a 40 minute drive every week which keeps the battery well charged. Batteries on the s type last about five years, and if not kept charged the electronics in the s type will give you a bit of trouble.
I think you will enjoy the s type - Grace, Pace and Space,
Regards,
Peter,