I have been researching into the question, "Can vehicles (cars) still pass an MOT Test if their original Halogen Headlights have been upgraded to either HID or LED Bulbs.
There seems to be an awful amount of opinion and conjecture on this subject. BUT, as best as I can find in a legal stance, it appears to be that any originally fitted halogen lit headlamp car first registered after 1st of April 1986, would still fail an MOT. As per Special Notice 01:21headlampt conversion.
Below are links to :
GOV.UK MOT Special Notice 01:21, which attempts to clarify the situation.
https://www.gov.uk/government/publications/special-notice-01-21-headlamp-conversions/mot-special-notice-01-21-headlamp-conversions
A long article by well known bulb supplier ABD , which seems a very comprehensive explanation of the situation.
https://www.autobulbsdirect.co.uk/blog/the-brightest-car-light-bulbs/
Personally I am NOT (and would not) suggesting that they should not be fitted (as that is a right of choice for every individual). However I do have an opinion that the offence is not in using them (as this would be very difficult to establish direct evidence at the roadside) but that the problem will occur when an MOT Tester finds these type of bulbs (again depends on how strict the examination is ). One thing I am sure of however, is that being the owner/user of a Jaguar S Type, it is not going to be easy for an MOT examiner to identify what actual type of bulb is being used by sighting (direct evidence) the bulb without time consuming (due to not easy access) removal of the backing to the headlamp unit.
This submission does not take any account of matters such as dazzle to other road users etc., which of course is altogether another discussion.
This legality (or not), is in my opinion, up to each and every individual to make their own decision. I have just attempted to provide some information which can be read and digested before making your own decision.
Best Wishes and Regards, John