It’s not just the illegality worry, if you do sadly have an accident in the UK, and the investigators determine that your lighting was not correct, you could be in serious trouble. And your insurers will run away.
Looking at the headlamps is one of the first things a crash-investigator does, e.g. they can learn a lot from how the filaments have deformed in a big hit.
I’ve been in this position, fortunately everything checked out perfectly, and I was the one who received the compensation, despite the outright lies from the other party.
Halogen bulbs still work very effectively, in properly designed reflectors. Are cost-effective, reliable, maintainable, and dissipate waste heat by radiating it out of the front so need no particular special cooling, nevermind dinky little fans etc. (Never a good idea, under the bonnet). Or risking cooking, melting, frazzling, crazing, or otherwise messing up your very expensive plastic headlamps.
Mature technology, which is a good thing.
Designers and stylists like the possibilities that other technology can deliver, but whether it is really progress is debatable. HID is pretty much dead, LEDs now tick the boxes, with LERP at the high end. And CO2 emissions reduced, allegedly (I’d like to see the whole-life analysis on that). At a price though. Even with the cheapest non-homologated unknown retrofit imports, nevermind a properly engineered solution.
I like halogens, although my main vehicle has some very fancy matrix LED headlamps. I just hope nothing goes wrong with them, or they get damaged, because that might cost more than the car is worth to fix, a few years later.
