How could I attach a face plate to a broken Appleby dry lining box?

An electrician has installed a dry lining box for a cat6 network terminal. These boxes are supposed to have a metal insert inside each of the yellow parts, which accepts the type of screw that is standard for attaching UK electrical switches, sockets etc. Unfortunately, both of these metal inserts are missing, so there is no obvious way to attach the faceplate.

I don't want to replace the entire box as the plasterboard has already been tiled.

What alternative methods could be used to attach the faceplate securely?

Somebody asked about removing the yellow inserts from these boxes on Screwfix, and Appleby responded that "in design principle and as a general rule these [yellow parts] should never be removed as the lugs themselves cannot be replaced." I hope somebody here can be more helpful than this.

Again, this is being used for networking — not mains — so electrical safety is not a serious concern.