Hi Josh
I've just bought a 55 plate S-Type V6 3.0ltr and what a cracker. Nice and smooth, quiet, powerful enough for me and very comfortable. In fact everything you would want and expect from a Jaguar. Mine's an auto, think the manuals are a little rare? Only filled it up once but that gave me 26/gal, my ZT 1.8T only averaged 28/gal over the 5 or so year I owned it.
As always advice is that you try before you buy and try as many as you can. Advice to me was the later the better, but with history. One of things to look for are the sills as these can be a problem area for rust, there's plenty on here though on that and other things to look out for. But take someome with you to view.
It will fit the bill. Just do it as they say.
Hope this helps.
Gary M