If it is a structural movement then it is going to be an expensive repair but If no cracks going across the room. I would take out the bead, cut out any cracks or loose plaster, PVA background, fix more screws if plasterboard loose, bed in new bead, Fill and sand area.
Get a local plasterer to...
My question is:
What interior insulation can I use that is cost effective? Because of the cement finish outside, lime is useless as it won’t breath? Can I dry line it with a 4 inch cavity and an insulated slab? Should I vent the cavity?
My answer is.
It’s only the facade that is listed, I can...
It is going to need bonding, then fit skirting and use Easyfill 60. You could replace with higher skirting to reduce the amount of filling and sanding.
Learn from you mistakes, think the job through before plastering next time.