I’m in exactly the same position with (by the sounds of it) exactly the same garage.
It was storm damaged, then vandalised, and now it’s in a state where there’s more hole than side panel and needs pulling down before it falls down (it’s basically the wooden uprights and a roof, bar a few pieces.
I spoke to the local tip “recycling centre” and was told that they could give me disposal bags to put it in; but that I couldn’t transport a shedload at once so I’d have to fill a bag, take it too them and they’d give me another to fill, and so on.
I’ve ignored it for about ten years now because frankly it gives me the fear. However, that link ^^ above for testing sounds like money well spent. Nice one.
Keep us posted as to how you get on.