Can I put a water butt on a neighbour's downpipe?

twopenny

I use a dustbin for the surplus water I collect from the house, indoors. Painted said bin to look better.

Small shed? You can use a chain attached to guttering and the rainwater will run down that into a butt, small pond or recepticle of your choice. Quick and easy.
From galvanised chain cheap to fancy drops.
Seems they make a whole smart effort for it now but a simple hole and funnel or similar will work.
They are called rain chains.