House survey advice

I have a narrow cavity in my 1910 house. The original ties were strips of steel (with holes punched in, probably some kind of offcut) with the ends flattened out into fish-tails. Over time, these rusted and expanded or broke. One wall had a pronounced bulge which needed to be tied back. Note that the external leaf of a cavity wall isn't a primary load-bearing one and can be merely "held" in place.

Seconded. I watched my contractor while he searched for and ground out the old ties. There were noticeably fewer the further up he went. Shoddy building standards are nothing new ;-)