My own experience after taking my 1971 GT6 for a pre-MOT inspection and having a chat with the tester.
The car failed only due to having LHD headlights fitted which I didn’t even consider, even though I had imported it from Stockholm it never crossed my mind. However I never use it after dark, then again you never know, especially now the nights are drawing in. So new headlights were fitted and re-aligned.
As for emissions, the tester was not really interested in any of the readings as again due to its age it was pre any emission standards. Knowing what the recommended readings should be, I ask if we could adjust them down so at least it is running nearer standard, they were adjusted as close as possible without affecting idle or it’s running condition.
My personal feeling is that it is always better to have another set of eyes to check over your car, your own thoughts on its condition may differ significantly to an MOT tester that does inspections for a living, even if you don’t go the full hog and have an MOT certificate, a yearly inspection doesn’t hurt.