Idiot alert 
I was thinking about, in place of the washer, some kind of hook with a hole on top for a screw. Like a washer with a hook underneath. I have no idea where to find that, but I might see if "ook" have anything.
The half nut is to pull it against the wall. The d-hook will fit over the pan head.
No, I get that, I'm saying to go back to JUST the bolt, hanging the mirror off just the bolts is not advisable?
I think it will just sag. It needs something to pull the metal bit behind the wall forward, to actually clamp it to the plasterboard.
That's what I thought... ok thanks your help is jogging my mind for what to do. The two sides are like this right now... see how they're a bit sagged? It's like 2-3mm
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local
