Hi and good luck with the search.
I bought an Elan S4 coupe some three years ago and haven't regretted it one bit. Mine is a Stromberg model and the performance is fine for what I need it for which is to take it to the odd show and a few decent drives through the British countryside making use of the superb handling that these little sports cars have. We have ventured as far as Jim Clark Museum from Preston so it's good for decent distances if maintained correctly.
?30k is enough to buy a pretty sound example in my opinion, nor concours but a decent looking and good running example. As people say try a few before you buy.
Paintwork is a subjective matter with these cars, they can suffer with microblistering, (mine does) but then I'm wanting more to drive the car not show it, so whilst the purists would tut and roll their eyes, I'm happy my car looks decent from 5 yards and excellent from 10 yards
Wiring is a challenge on these cars as noted previously, but if you are familiar with old cars and comfortable working on them then I think that is half the pleasure of the car. Buy something that is decent to start with and keep the car on the road and make upgrades as you go, from history I believe there is nothing worse than buying a car then starting a major restoration and missing out on the driving aspect of Elan ownership.
If you are not a club member then I would suggest finding out where your local Lotus owners gather, go meet with them and pick their brains, looks at their cars and you never know one or two might let you have a drive so you get the full experience, even riding in the passenger seat will help you understand what to look and listen out for.
Spares are plentiful in the main although again there are some parts classed as unobtainium, however, that should only affect you if you are looking for a show car, in my experiences to date I've found there are always parts available and alternatives to be had if you are not overly fussy about originality.
Last, and probably most importantly, read as much info as you can from books and here in the forum, the car owners on here are a fantastic group of people with a vast amount of knowledge and expertise which, importantly, they are willing to share.
Have fun seeking out your dream car and once purchased enjoy the living daylights out of it