I noticed the same firm, AA Bill, are doing the same in Forest Hill based on this thread on SE23.com.
AA Bill seems to be the company. There's the one on Canonbie as mentioned, one on Sydenham Hill, and one outside the Livesey hall near the Savacentre.
I see it as anti-social business practice, same as the D&M Van approach to taking from the community. Others who post seem to think it is a fine part of Olde Brockley heritage!! Or part of a glorious class struggle?
Worse still - their overuse of apostrophes is presumably responsible for the missing one in Brockleys Rock.