I think this is in the UK folks (OP please verify). Is this a council issue as well ? Laws vary country to country and this is an international site.

I'm a little unclear after your last post. How many houses are involved? I count at least three. The 2 with street frontage on either side of the passageway and the third without street frontage. Also it now appears that this is not just an alleyway, but a gated passage between the 2 houses. Were you given a key to the gate or just to the side door that opens on the passageway? When you leave the trash bin, did you leave it in the passageway or on the street? Do the trash collectors have a key to the door to the passageway?

In any case I think you over-reacted to the solicitor's letter. Just leave it to the landlady. Also I don't think this is sufficient reason to break the lease.