It was painted with Frosts manifold paint (only one type listed in their catalogue. It has peeled off some of the galv where I haven't 'keyed' it particularly well but I'm not fussed.
Thanks for the comments chaps, I didn't hold much hope of it working tbh, just making the flanges took long enough - holesawing through 6mm steel isn't easy, but I'm lucky the old man has one of those really old quality pillar drills. I'm just pleased it works and we managed to keep it all straight throughout the welding process.
The only thing I forgot was a bung for the lambda sensor for the Meqasquirting