Erm, off piste suggestion but - mine passed three MOTs before the fourth MOT tester failed it and told me why the brake lights weren’t bright enough.
It’s laughably easy to insert the bulb holders the wrong way round into the back of the light cluster. So my brake bulbs were sitting behind the reflectors!!!! Check they are the right way round before going to spend on brighter bulbs.
On that note, I went LED to reduce the load on the alternator. But they are not brighter, just more instant and less load on the wiring etc.