Interesting article in Practical Classics (December issue) about the above. I've considered replacing some of the rear and smaller lights with LED replacements BUT....
"UK rules state that lights on all cars first used after April 1st 1986 must have Approval Marks, which means filament bulbs MUST be fitted (unless LED ones came as standard fitting). However, for certain items, the cut-off dates are much earlier; for front sidelights the dates is January 1st 1972; for rear side lamps it is 1st January 1974 and for brake lamps it is 1st February 1974. No LEDs should be used for rear fog lamps at all."
It may be worth stocking up on filament bulbs now as it seems we are racing ahead with modern cars all being fitted with LEDs as standard, thus avoiding the need for Approval Marks.
In reality, I can't imagine an MOT tester taking the lens covers off to see what type of "bulb" is fitted. The article does state that, in most cases, the LED lights will offer better illumination (and they'll probably last a zillion times longer, methinks!)
Just spoken to my MOT guy as I had the 160J in for a repair and he tells me that checking the markings etc. on the lights is NOT part of the MOT procedure....so long as the light works it's okay. Horses mouth etc. etc.
gotta say i hate those LED replacement bulbs. they're awfull at providing a decent light output at any angle other then face on. IMHO they are not an "upgrade" they're just dangerous.... Proper light units designed for LED type bulbs are fine, but fitting bulbs into light housings not designed for them is not a good idea.