Great photos, and more mancunian old brickwork.
Surprised UU have not put a "safety chain" or some form of barrier and warning signs ahead of that scary looking slope into an unknown doom...given H&S is such a big issue in the UK right now, this seems a bit negligent don't you think?
In HK where I am now, I tried to get into one drainage tunnel, the manhole is locked ABOVE, and the grille only lets you look in, but not climb in?!