The regulations seem to have changed again:
From 22 March 2021, we’re changing these rules so that not all motorcycles and vehicles will fail the MOT test if their halogen headlamp units have been converted to be used with HID or LED bulbs.
Class 1 and 2 motorcycles must not be failed for the defect ‘Light source and lamp not compatible’.
Headlamps must comply with all other requirements of the test and headlamp aim.
The motorcycle inspection manual will be updated shortly, and the ability to select the defect within the MOT testing service will be removed.
For class 3,4,5 and 7 vehicles, the defect ‘Light source and lamp not compatible’ only applies to vehicles first used on or after 1 April 1986.
Should a vehicle be presented for an MOT test with conversions before 1 April 1986 they must not be failed with immediate effect.
Vehicles presented with converted halogen headlamp units first used on or after 1 April 1986 will continue to be failed.
Headlamps must comply with all other requirements of the test and headlamp aim.
https://www.gov.uk/government/publications/special-notice-01-21-headlamp-conversions/mot-special-notice-01-21-headlamp-conversions