In reply to druss:
The reason you are having trouble finding “trail race certified” outerwear is because it is a completely made up concept. Googling brings up this thread. The nearest you will get is the FRA (Fell Runners Association) guidance, which certainly isn’t certified in any way. The FRA guidance is basically waterproof material, taped seams and a hood.
Ive got an expensive innov8 race jacket, it is OK, but no better than the £34 Decathlon sale jacket that I bought my other half and actually in the sort of conditions where you want to be wearing a waterproof, a £10 waterproof does what you need.