MOT Testers have a regulated poker for proding suspect areas.
How can Hammerite be a bodge? Filler, fiberglass and seam sealer is a bodge!!!
I've been getting old borderline mini though MOT's for years - But what do I know!!!
If you were not concerned about the level of corrosion and felt the metal was strong enough why would you need to paint it and distract the MOT tester from it??
If you feel the need to hide it with fresh paint in a hope that the MOT tester doesn't see it then you obviously dont feel the car meets the miniumin requirement to pass an MOT!