In reply to:

So, what do you call bin bags then (black plastic bags to line dustbins/trashcans)?

plastic trashbags
plastic liners for the trashcan
trashcan liners
50-gallon liners

...and so on. But never binbags! Ha! Binbags (I must not hyphenate because:) sounds so funny! It is a very comical-sounding name. If I were a writer for TV, I would definitely work binbag a lot into my scripts just for the sound of it! Now 'plastic liners'? No humor; no fun. Just functional. Blah!