First, before buying any E type do research research research. And then do more research. A good E type is a delight. Any of the 3 series of cars has their charms. They are not all the same by any means. The "early" series 1s have some distinct idiosynchrasies. Like the boss mentioned, not so great seats (unless you happen to fit them) A different brake booster system, and the earliest cars have flat floors, out side locks for the bonnet and the like. The flat floors were changed by the factory to dished ones to enable actual humans to drive them. The later 4.2 cars have most of the bugs removed, and are to me more drivable.
Series 2 cars are even more drivable, with better cooling systems, and if you wish, AC, power steering, and auto trans on the 2 plus 2s. They have a bigger mouth on the bonnet, larger relocated tail lamps, and are not as pretty or pure in form.
The series 3 V12s are another beast altogether.More of a Grand Touring car than a sports car, they have much better interior room, (10 inch longer cockpit) are smooth as butter, and almost as complex as a Ferrari. A good car is a great car. A bad one can ruin you.
The whole thing about E types is 1. Condition. Any rust is too much, Leather is expensive to re do, the front frame work can rust, and is not repairable in real life. New parts are $$$$ Even changing a clutch is a big dollar job. Replacing a damaged bonnet can easily take 10 grand before it is perfect.
The second thing (assuming you want it at least partly as an "investment"), is that if restored, is it correct? A lot of parts can be mixed and matched, and the car will work fine. To make it correct may take finding some hard to come by little bits. Repro parts are not as good as the originals (IMO anyway) Contact your local Jag club, and try to get a ride (or better yet a drive) in a car that is at least similar to the one that you decide on. Have a pre purchase inspection done by someone that knows the cars. A good e type is a truly great car, hard to believe that the design is almost 50 years old. A poorly restored car (I call 'em cosmetic clunkers) can be a major financial pit. So buy wisely, and buy the best car you can afford.