Alex,
I assume that this thread title is chosen for one of two reasons - either you are based in Norfolk, and seeking an S2, or you are specifically seeking a Norfolk Mustard (yellow) S2.
If you can add your location to your profile (or the thread) it may help, also if you are looking to buy 'locally' or prepared to travel. Everyone has different expectations in these matters, and there is no right or wrong answers.
My first elan was bought from a bloke 3 miles from my house, the second required a couple of trips to Norwich, and the third towing a trailer to Oxford - obviously, the further you are prepared to travel, the wider the selection pool.
Budget is another consideration, and I wouldn't presume to tell anyone how much they should spend on these things (although I often have a bit of a clue as to their actual "value"). Anyone who has watched the market in the last few years has seen it change only a little, but the really cheap cars no longer exist as most have been either broken for parts, or restored (although they do surface from time to time).
There are 3 basic categories left - (1) Completely original, well maintained cars........ (2) Renovated/Restored cars which should be good for another 30+ years..... (3) "The rest" - ie, owned and used regularly, but maybe only actually 'repaired' as opposed to 'preventatively maintained'....
Cat (1) are few and far between - and not often for sale..... if they are, it is usually through a 'known-to-be-good' dealer - anything for sale by Guy Munday is likely to be in this category, and certainly you will get a knowledgeable seller.... but priced at a suitable premium.
Cat (2) tend to be in the ownership of people who have had them for a while, and 95% are not even considering to sell. Ones offered by a 'good dealer' (SWLPC etc) should be in this category, as they tend to sort out absolutely anything likely to be amiss before selling their stock. Otherwise, the owners have simply got to the life stage where the Elan may no longer be suitable for them (physicaly, emotionally, or because of downsizing of property)
Cat (3) make up the vast majority of cars for sale - and not just in relation to Elans, it applies to any car really. These are the ones for sale from a 'local' car dealer who has bought it cheap and wants to make a few quid - often spending 'just enough' to make it look tidy and drive fine for a year. (not a bad thing, but just be aware of what you are buying!!!). Or a private owner who has bought a car, maybe finding it isn't for them and selling it again. In which case it may be a year older, but not had any money spent on it in that time (or only the minimum). Or those who don't realise the time and/or money it can cost to keep one up together..... maybe they have spent a fair bit, but then realise that it could take another fair bit to complete the 'niggles' (to turn it into a Cat (2) car).
The point of my answer is that there are people who will tell you that Elans are worth £2-3K, because that is what they paid for theirs 20 years ago, or have been buying up the 'bottom-of-the-market' stock for spare parts.
There are those who will tell you that Elans are worth £15K because that is what the top dealers are asking, and it is what many of us have as an agreed value on our cars, as we know that it would cost that to replace them if anything untoward were to happen.
There are those who will tell you that Elans are worth £6-8K as that is what the majority seem to have as a price on the adverts - but it's always a bell-curve with some cheaper and some more expensive.
Much of my advice is common to everything, but some is specific to the Elan as I feel that I know the car(s) fairly well, and the cost(s) of maintenance/ownership..... BUT.... it is still only a personal opinion, so feel free to take or leave it as you wish - it is certainly worth every penny that you have been charged for it!
What I would say, is that many people seem to feel that the S2 is a 'better' car, so only want to buy those versions - however, as even the newest S2 is still 30 years old, they cannot be judged on age alone. My advice is to consider any Elan, and buy the one which fits your requirements.
I fully appreciate that the S2 had over 100 changes from the SE - but there certainly were NOT 100 'improvements'. The choice of colours is greater (but if the car needs a respray anyway, you can have it whatever colour you desire). The seats are in a bigger choice of colours - but again, can be replicated (later SE's had really nice perforated leather seats which I find more comfortable than S2 seats as they had a more 'springy' base.... some people like the early striped seats, some don't - some even prefer the half-leather seats).
The cloth hood is a better design, the rear wishbones are galvanised - both of which have often already been upgraded in the earlier cars as the originals are usually well past their best by now.
On the 'negative' side, because of the age, there is a Cat Converter which robs about 10bhp - and puts the car into the tighter MOT regulations, which may or may not be a concern dependent on the specific car. Certain parts of the interior were re-manufactured with materials which were not as robust as the earlier cars (hood header rails are a common item needing repair/replacement) - the centre console has no storage box - the handbrake has a 'collapsible' design which can be a little disconcerting.
The 2 biggest 'reasons' to go for an S2 are (1) the wheels - maybe not a huge thing, but they are certainly considered to be 'desirable'..... and (2) the steering wheel - if the original owner specified the Nardi item - a lovely thing to behold - but again, these things have often been fitted to earlier cars anyway (or can be).
So, my actual advice, is to buy the best car you can within your budget, but expect to need to spend time/money on it.... don't worry too much about the age/mileage (within reason)..... drive and enjoy it!
If you are a reasonably confident/competent DIYer then there is nothing that you will not be able to attempt yourself - much to the chagrin of some people, I have even been known to say that it is only a plastic Astra in a pretty frock - which is to say that the mechanicals are pretty much as per any GM car of the era, with many shared parts.
By extension, the car is not beyond the reach of pretty much any good local mechanic, and certainly doesn't "need" a Lotus dealer to look after it (although there are many owners who use a known good independent specialist as sometimes the knowledge is specific to the car).
By asking on this forum, you are assured of a seller who knows a bit about what they have, and have had access to the very best advice on the internet for these cars.......
....... and if you are prepared to travel to Castle Combe on Saturday (or down to the West country any other time), either Jonathan or Mike's cars are both worth their prices
