Joao and John are both correct - and I'll add on a bit more (purely opinion, from my own perspective).
I don't know why some people value the S2 far higher than an SE (or NA) - any age-related issues are equalled out by the passing of the years, so it leaves the actual 'differences' between the two to consider..... yes, the S2 has nicer wheels!... it has galvanised rear suspension arms and an improved design of the upper link.... it has a better design of rain channel in the soft-top...... it comes in a larger variety of colours.
BUT
It has weaker plastic trim pieces around the hood...... it has a catalytic converter & pre-cat (ignoring the 10BHP loss, I was actually thinking of the extra complexity/costs)..... it has an alarm system which (if still fitted) is of an age that it can leave you stranded....... if you lock your keys in the boot, you're a bit stuffed.
So, there are a load of other differences, but not all are improvements. Many of the well-maintained S1 cars have has the later parts retro-fitted (suspension, maybe wheels, hood etc as part of ongoing upkeep). The later S1 cars had the improved seats that you find in the S2 (well, nearly the same) and the extra colours are irrelevant when many cars have had or need a repaint anyway.
So, I always advocate to get the 'best' you can find for your budget (or requirements) - and don't fixate on age, colour or mileage....... but some people find those things important, so who am I to dictate?
We have all seen people who want to buy a "low mileage S2 in yellow with magnolia leather"..... and such a car will ALWAYS find a new home quickly, whilst a Pacific blue SE with half-leather and 100K miles will be seen as a 'worse' car to own, and command a much lower asking price.
To me, that's really odd - as the SE may have had money spent (or may not), so has a value that needs consideration. Just the information given will offer no clue as to a fair price - and even photos don't help much.
Anyway, my real point is this:-
I know of a few dozen really, really great elans out there, and any one of them would be a good car to buy..... but that's the thing - NONE of them are for sale, or are ever really likely to be. They are the cars which have been in the same ownership for many years (often since new, or nearly new). They have been meticulously maintained, or restored (or both) by enthusiastic owners. Many have done the work themselves, some have paid out a small (or large) fortune over the years. I know what sort of number the owners put on the insurance valuations, and I also know that many could not be replaced for that price..... although it is very possible to buy another elan for that number..... if you find one of these, better grab it quick before someone else does (Yes, Mark, I'm looking at you

)
Then we get the 'second-tier' of elans - those which have been bought, had money spent, and enjoyed by the owners for a long time. These are also great cars to buy - BUT come up for sale rarely. If they do come up for sale, they are often snapped up by someone who they know (we get them up for sale on this forum from time to time, and they don't hang around for long).
Next, we have the ones that were bought by someone who needs to scratch the itch of owning one - maybe a neighbour had one as they were growing up, or they played games on Amiga computers, or whatever - if they fall in love with the car, it will get elevated to the group above, but if not, after a year or two, it will be sold on when the reality overtakes the love. These are often good cars to buy as many such people lavish a sum of cash on the new purchase, which they don't get back when they sell it.
There are the 'constantly for sale' cars we see....... they appear of ebay (or somewhere else) and someone buys it, then a month later, it's back for sale at a higher price after it's had a wash, then it sells, the new owner realises it isn't that great and sells it again, and so it goes round..... these are where the danger lies for new owners - they could be worth anything between £2k and 10K - and the price ticket will be in the same range, BUT not necessarily correlate to each other.
Then, really occasionally, we get the "i don't know what I've got here" cars - you know, the real bargains...... often sold by a relative of an "estate sale". They have a tier 2 car (or even tier 1, except someone else will have snapped it up) which they offer for 'everyday car' money as that is what they're lead to believe it's worth.... and someone gets a bargain.
I have seen a fair few of these over the years, and always try to suggest them to people who are actively looking for a car - often it isn't the colour they want, or the model they desire, but it is nearly always the "best buy" they could make - and the rest can be changed.
IMO, it comes down to what you want - if you want to park in a field with a shiny car to show to other people, your requirements are different to someone who wants to blast round a race-track every weekend. If you want to do 2K mile tours round Europe you need a different car to someone who needs to commute 8K miles a year in all weathers.
I used to commute in mine, I have been on the European tours, I have done the track stuff, and even parked in a field to show it off - I KNOW that the car can do it all, and I know that the requirements change over time. The condition of the car now is vastly different to when i bought it, as it was changed for track use, changed again for constant road use, etc etc now it enjoys a cosy life inside a garage (it used to live outside at my old house when it was being used daily), and comes out when I want it to.
So, what is a car worth? don't ask me - I really don't know!
Okay, so I know how much all the parts cost to do a pretty total restoration (been there, done those)..... I know what a respray may cost (except they change all the time)...... I know how many hundreds of hours it adds up to...... I do it all myself, so have no labour costs to consider (except paint - I no longer have the facilities to spray complete cars)..... if I added up what i spent last year and paid myself £11/hr which is the 'living wage', I would have a far higher price than anyone would give me for the car I restored..... but that's okay, because it isn't for sale anyway! Even without adding in the labour, there are those who wouldn't see may car as being as "good" as the mythical "Yellow S2" - but I know which one I'd rather be sitting outside waiting for the trip to Europe, or down to the beach, or to the track.... and it will be able to do it for many years to come as all the effort has been expended already.
So, buy what you want, pay what you think is fair, and expect it to cost money/time afterwards to keep it up...... otherwise you end up with the lowest category of car :-
The 'just about kept going' banger - you now, the one which struggles through the MOT every year, needs bodywork, interior trim, and engine rebuild, replacement of parts etc etc (this is NOT just an Elan thing - it's every car out there!). They are unloved by everyone who owns them, but they won't sell it because they believe it's an "appreciating classic" worth £10K, and no-one will offer them more than £2k as a breaker.
(oh how I love to buy them for the 'breaker' price and then restore them because I'm some kind of stupid idiot - but there aren't that many of us left)