It does seem unfair that the type of conversion bulbs sold by Classic cars leds , which appear to be an improvement in every way, are now illegal because of the dangerous characteristics of some other conversion kits on the market. But its an MOT fail to convert headlamp units made for halogen bulbs to run Led or HID/Xenon. And remains illegal whether or not the tester turns a blind eye or you swop bulbs just for the test.
I am not averse to bending the law slightly on occasions if the result is actually safer and the consequences of being caught might just be a small fine. But as pointed out there is no way your insurers would approve of a modification that makes your car illegal. They would be only too pleased to find a reason not to pay out a claim for many thousands. They wouldnt care if its was intentional on your part. And the chances of them finding out might be higher than you think. The other driver only needs to mention as part of his excuse that your unusually bright lights blinded him , or if the car is damaged enough its towed away and an engineer appointed by the insurer notices the leds. If the crash was serious enough police crash investigators would also notice. (they can even tell if a bulb was lit at the time it was smashed - the filament fuses ) The courts might take a lenient view on its relevance to the crash but your insurers will be rubbing their hands with glee.
But i have found a much greater injustice. You can legally fit led and Hid bulbs and pass the mot if you change the whole headlight units for ones made specially for that type of bulb. A very expensive option but might appeal to customising enthusiasts. Most replacement headlights just take H4 bulbs, but I found the following described as "cell rim' I THINK that means they are led. And they MIGHT be legal, Might pass the test MOT beam pattern test, the tester might be satisfied the unfamiliar markings means its genuine led, not converted and MIGHT be accepted by insurers as a modification. Caveat Emptor - Buyer beware.
https://www.car-parts.ie/car-parts/abakus/p-9259593 384 Euro (£330) (Ireland)
or the same things
https://www.autodoc.co.uk/abakus/9259592 £427.39
(IIRC they were even more expensive when I had a quick look yesterday)
Prices per pair, but without bulbs, or wiring connectors.
But crucially both sellers are the SAME company. Autodoc in Germany. Whats that all about? Brexit freedoms ? (would it be too political to mention that the Liz Truss post Brexit Trade deal with Japan has resulted in fewer UK exports to Japan,not more as promised)
Its a shame. i used Autodoc for some brake discs pre brexit and delivery from Germany was fast and the price good. .