If you report the signs as fly posting on Love Clean Streets there is a chance they will get removed - some of the ones around the centre of Forest Hill have apparently been removed in that way already e.g. here, here and here.
Given the number and frequency of these signs, hopefully someone in LBC will have a word.
Thanks for suggesting this! I reported two signs for the trees on Dartmouth rd and they’ve been removed in less than 24hr. What a great service
They’re actually locking them to railings with bike locks to make them harder to remove. Good to see Clean Streets working so efficiently.
I do hope the bike locks are being angle ground and fines issued
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They looks like pretty cheap cable bike locks, so a pair of bolt cutters should do it easily, as evidenced by a cleanly sliced-off lock I saw on Queenswood Road the other day 
Hopefully their Christmas trees are better quality than their signs!
Initially I thought these signs were like Pokémon popping up everywhere to be captured in the Love Lewisham app, but now I notice that it’s turned into whack-a-mole as some of the signs have come back!
The council should be clearing up these tacky signs and issuing fixed penalty notices at £75 a pop. That would pay for a few more Christmas lights on the high street.
We got ours from @Shannonsgc today - always nice to see the team in there and have a quick chat, as well as coming away with a great tree of course!