That stuff looks good, but cyanoacrylate adhesives have two issues
We use them at work extensively for all kinds of stuff. In some cases we use the spray-on accelerant but then it it goes off really fast (seconds). The extent of the vapour issues varies according to the adhesive and there are “low bloom” variants but AFAIK none of them can be used in a totally confined space.
So, given that one cannot reassemble the assembly immediately after gluing and subject it to fuel immediately, IMHO the main advantage is that you can buy this stuff in a small bottle, rather than spending £30 on a PR1440 semkit and throwing away 99.9% of it. OTOH a lot of Loctite products do cost £30 for a tiny bottle 
I think that for fuel fittings one needs a 2-pack solution of some sort; one which doesn’t rely on air or lack of air to cure and one which self cures even in a decent thickness.
Is there a fuel proof epoxy resin?
Quick check on Loctite website – looks like 567 PST well suited to the task ?
Locktite 565 PST or 567 PST works well. Wipe off the excess that is exposed to air, as Peter notes it won’t dry like the material that is sealing the thread. You can buy it at auto parts stores in the US for about $20, enough to do several jobs. Mainly for that reason I use this or the Permatex equivalent.
Is there a fuel proof epoxy resin?
There certainly is, such a product was used to repair my leaking fuel pump. Would have to ask for the details, though. The repair was done two years ago and is still ok.
JB Weld is a two-part filled epoxy product that is famous in the US (notorious? infamous? ) for being able to fix just about anything, engine cases, fuel pumps etc. Great stuff around the farm The funny thing is that it really is quite capable and has no problem with fuel… unless the fuel contains alcohol in it in which case who knows for sure.
“When fully cured, J-B Weld is completely resistant to water, gasoline, and about every other petroleum product or automotive chemical”
This underlines just what a tricky area this is…
A lot of materials are OK for days, or weeks, or months, and then what happens? In an aircraft fuel system, the exposure to fuel is continuous and lasts the life of the aircraft. There are filters along the fuel system but some of them are designed to relieve above a certain pressure so if e.g. you turn on the electric fuel pump, the debris could get washed further along and you never know where it will end up.
The PR1422/1440 “30 quid throwaway semkit scam scheme” might be annoying but in the grand scheme of things, 30 quid is nothing.
Re alcohol look some time at the recent history of plastic fuel tanks on motorcycles. With alcohol in the fuel they’ve had a history of bubbling and warping until they don’t fit the frame, but when alcohol is never put in the tank there are no problems. This was well established with Italian motorcycles being sold into the U.S. market during the long period before auto fuel in Europe contained any alcohol. Also, and oddly enough, if somebody in the US moved to an area where alcohol was no longer in the fuel, the warping and bubbling under the paint would to some degree reverse. Toluene and other constituents may we’ll be a problem too, but it was alcohol that was demonstrated as the problem in the above situation from circa 1997 until roughly 2013 – by which time the manufacturers finally redesigned all the afflicted bikes or (better) went back to welded metal fuel tanks. The worst example might be the GT1000 Ducati, on which owners were getting maybe two years between very expensive plastic fuel tank replacements.
Assuming they still wanted to use cheaper plastic tanks, the manufacturers solution was to change the material used to make the fuel tanks. With those plastics they could no longer be painted, meaning an additional painted plastic cover now needs to fitted on top of the unpainted alcohol resistant plastic fuel tank. As a result the problem didn’t get solved for years until a new model was designed, particularly as it was far off in the US where problems were occurring. Out of sight, out of mind.
Meanwhile in the aftermarket people have gone into business lining the existing tanks, and compounds have been found will do the job even on a old polyester resin fiberglass tank . Newer epoxy resin fiberglass tanks have not typically been a problem, at least not like 70s style polyester resin fiberglass tanks that will literally dissolve in modern auto fuel.
Re sealing pipe threads, it’s just not that big a deal for the reasons I described earlier. If you’re sealing a whole wet wing, then you have a much more critical situation requiring the use of Pro-Seal etc.
I remember discussing this fuel problem in the late-80ies with Ducati bevel type owners and their leaking (polyester?) fiber glass tanks. At that time no alcohol was used in fuel, definitely. But fuel composition had changed and more so with unleaded, LONG before alcohol was added. So I still say alcohol is not the problem being NOT very aggressive to most plastics. Whiskey distilleries would have been very challenged for ages if it were so – and I would NOT drink that stuff, – but I don´t anyway. Again I suggest to do your own test, it only takes a few days to watch swelling NBR seals in auto unleaded, but NO change with ethylalcohol/white spirit. Don´t know about methylalcohol as used by speedway machines or model aircraft, but that is typically not added to auto fuel, being very poisonous and too expensive for fuel. I am using one pack polyurethane paint for sealing fuel tanks and that is OK for almost 30 years of unleaded auto fuel – OK for a long time test ? People tend to blame the alcohol to be the demon but in fact all sorts of cheap chemicals are added for fuel that challenge the fuel system. And that long before alcohol was subsidised for fuel. You don´t find much or no alcohol in our Super fuel because it is more expensive to add to gasoline, still you get the chemical attacks !
Vic
