Radiator: Copper transfers heat better than aluminum. And copper radiators are easier to repair and have a reputation for being less prone to cracking from fatigue compared to aluminum. For an aluminum radiator to be "more efficient" than a copper one of the same dimensions (as some claim to be), the aluminum one will need larger diameter tubes with thinner walls (making it more fragile?). So copper all the way.
I think the main reason for aluminum, whether in mass-produced cars or in racing, is that it is less expensive. Of course it gets the job done, but in the Esprit S1, where you have an insulated fiberglass clamshell over the engine (lol 🙄) and a long, skinny radiator without many rows, you are looking to improve the margin of heat transfer any way you can.
Coolant: I don't see the point in Evans waterless coolant in a car like the S1. My understanding is that its ability to transfer heat is significantly less than that of 50/50 water/ethylene glycol. Again, that is going the opposite direction of what benefits the S1 the most. There is an argument here that one could better prevent the clogging of the radiator using the waterless coolant (less prone to scale/corrosion), but regularly flushing your cooling system and using distilled water (or maybe completely flushing it and changing over to a modern lifetime coolant) goes a long way in the same direction; there is a trade-off, but I think normal antifreeze is comfortably the winner here.
Fans: I have always used the stock fans. Every S1 I have owned has had either three or four. I rewire them so that they are fed a clean (10-guage to minimize voltage drop) power supply from the battery, each has its own relay (3 fans) or fans 1 and 3 have a relay and 2 and 4 have a relay (4 fans), and of course the load isn't carried through the otter switch. I did drive an S1 in Miami for a few years, and my blue S1 (454H) was "Florida-ized" by its long time previous owner in Tampa -- both with stock fans (3 and 4 respectively) and no issues. I see enough 95F degree days in Ohio . . . the stock fans move a lot of air. When someone can compare apples to apples, Spal (or some other brand) vs. stock, on current draw and cfm of air moved, I will seriously consider them . . . as long as they aren't the ones where you put bolts through the fins! That seems to me an unnecessary risk of failure, especially on our cars with their above average vibration.
I haven't seen any evidence that Spal or any other particular fan are actually better. If they do move more air, is it needed? (I haven't seen a need myself) . . . and at what expense of taxing the alternator/cutting into hp? Again, I would consider aftermarket if demonstrated to move more air while drawing fewer amps. Like with aluminum radiators, I think aftermarket fans are just popular because they are available, affordable, and do the job. Fine if you don't have any fans at all or your originals are not rebuildable, but I wouldn't seek them out without consideration of other variables.
Back to the Radiator:
When you re-core the radiator, see if they can add more rows. Think about this: Most cars with a similar surface area of radiator to the S1 have twice as many rows with half the length. Same cooling area, but a fraction of the resistance. The rows in an S1 radiator get clogged up easily, as they are long and few, offering greater opportunity for deposits. When people have cooling issues with their S1, they start doing all kinds of things like installing a lower temperature thermostat (does nothing to address overheating), adding a manual fan switch (also useless), flushing the system (good), buying aftermarket fans (placebo?), and cutting/adding a variety of vents and holes in the clamshell, body, etc. (ugh) . . . they'll do all kinds of things but won't do anything about the elephant in the room: the radiator.
Probably because it is the most expensive thing and they want to try all other options first.
Add to that that it is a lot of work to replace the radiator -- removing the spoiler/shroud, etc. . .
And they are probably looking at the radiator on the outside and it looks nice and clean; they think it's fine.
But the radiator is most often the answer.
It might look fine on the outside, but as stated before, there aren't a lot of rows, they get clogged or restricted more easily due to their length, and even partial clogging of a few of them significantly reduces the cooling capacity, because a tiny blockage affects that whole long row, which is significant to the overall cooling area of the radiator.
Every time I have an S1 radiator re-cored, I am blown away by how cool the car runs. In stop-and-go traffic, 90F degree summer days, in the hot sun. I am surprised by the fans' ability to bring the temperature down to where they shut off again. And then you *don't* want a lower temperature thermostat, because the engine and oil don't even get up to normal operating temperature on cooler days.
Plenty of people have bought the whole kit and caboodle -- aluminum radiator and aftermarket fan kit -- and say it works great. No doubt it does the job well. Any new radiator will be a massive improvement over an old one full of deposits. But just taking the physical properties of copper vs. aluminum and water/ethylene glycol, it seems to me the winners on heat transfer (giving the S1 a bigger margin on what it needs most) are copper and water/ethylene glycol. The benefits of waterless coolant don't outweigh the drawbacks in the case of the S1, and the only apparent benefit of aluminum is price.
By the way, you can often repair a non-working original Lucas fan for a few dollars. Most of the time when they fail, it is because the motor brushes have worn out. Take the motor apart, clean everything, replace the brushes, put a drop of oil on the bushing, and put new sealant in the appropriate areas when you put it back together. Take a few moments to spin the fan blade by hand to make sure they are all twisted the same amount.