Tim H, There has been a lot of chat about LED lamps on other classic car sites with warnings that in some circumstances, they are deemed to be illegal due to the lack of an "E" rating and therefore one could fall foul of the MOT. I haven't found a definitive answer yet and I keep on trying, any ideas please?
As far as I'm aware the level of illumination from a bulb is left to the tester's discretion as to whether it is adequate or not. If anyone has got documented evidence of an MOT tester removing E-marked light lenses in order to check that the bulbs are also so marked, and failing the car as a result I would be very interested to see it. The internet is full of people who love to pontificate endlessly over issues that which for any normal human being would be considered completely irrelevant.
The only comment I have ever received from a tester (and I always make sure I am present during the testing process) was a couple of years ago when he looked at my wing sidelights and said "They are a bit bluish, have you put LEDs in there?"
When I replied yes, he said "Very sensible. Anything that helps visibility in these cars is good".