I feel it probably makes more sense for location-specific instances to have their own communities for these things. So for example, have a Lemmy instance for London, e.g. london.lemmy.uk. Then have ~Freecycle@london.lemmy.uk community, which is for Freecycle posts in London.

Of course anyone from other instances can join, it just seems to make sense that something so location specific should be in a location specific Lemmy instance (of which there are a growing number).