Okay, I do realise that posting the same goddamn head three times in a row isn't making my blog any more exciting, but this is important! Kinda. I've just baked the details on to my retopo mesh and it looks just like it's supposed to. (ignore the neck, I'll bake it once I make the body) Before I used to make my lowpoly mesh in max, add the detail in Zbrush and then bake it, and for some reason this would always leave me with problems, areas losing detail or random artefacts. Perfectly fixable with Photoshop, of course, but still annoying. With retopology method, the end result looks exactly like the original sculpt.
I'm not sure if I'm happy with the mesh without the normal map - it doesn't look as defined as it should, despite the decent polycount. But I guess if I work on my topology a bit more, I'll do a better job next time.