The Hole-in-the-Wall Gang is a joking reference to any bum that hangs around a cash machine, ATM, or 'hole-in-the-wall'.
The name comes from the infamous Hole-in-the-Wall Gang that operated out of Johnson County, Wyoming during the late 19th century.
Why these beggars ask for spare change by a machine that'll only provide notes of £10 or more, is generally not understood.
Steve: I'm gonna get some money from Royal Bank.
Dave: Uh-oh, there's one of the Hole-in-the-Wall Gang...