Usually the Clanks and scrape nosies come from the Firestation often in the middle of the night- to accompany the police helicopter that hovers over Union ST and Southwark Bridge Rd.
Other than that it is the ghost of Chritmas Present
I think the horrible clanking noise is when they are doing something to the railway tracks , maintainance etc . When I used to live in Rotherham Walk it used to wake me up and drive me mad at times . I would still give my hind teeth to be be back though !!!!