This was a quick visit with NickUK and myself. In retrorespect it really isn't worth the effort.
Big Humpty, as seen below, is more of an undercrossing than a drain, with a length of maybe 50m. Its shape and size, the origin of its name, is a pleasant feature though. It is located upstream from the Medlock culvert, inbetween which it flows through the graveyard in a concrete channel.
The Minger is a massive storage tank with integrated overflow chamber. Accessed through a gate that is regularily broken open by the local pikeys, you have to crawl through a tiny pipe pictures at the top. After roughly 50m you enter into a huge chamber.
Pictures I had seen from there had always made the system look relatively clean, which made me want to go there. Unluckily this wasn't the case when we visited, with random "foam" flowing through it. Breathing was difficult, the eyes stung, and photos were a real struggle due to the moisture in the air.