Thanks a lot Dingo
That's cleared a lot of things up.
So judging by what you're saying, and what's in that guide, it would seem that - headlights aside - when it comes to tail-lights, indicators, etc, that an MOT tester is looking for basic functionality including colour etc of light, and the type of light isn't considered in itself.
Headlights - that's a different matter, because they have parameters of light shape and direction, and unless the headlight unit was designed for LEDs, with the lens etc, then there's always going to be a problem.
So it would appear that - other than headlights - if the LED replacement was functionally similar - eg - brightness, colour etc, then they will pass an MOT and would be acceptable.
The MOT guideline doesn't mention anything about type of bulb, it concentrates solely on functionality.
But what about this document
https://www.motoringassist.com/motor...ght-bulbs-car/
and why do Halfords have 'off-road use only' on their LEDs?
* Also - if you are using equivalent replacement LEDs bulbs, what type did you use because there's so many on the market, some over-powered, others under-powered.
John