Retrofit of gable wall restraint strap

I understand that you have cut the restraint strap and have approximately 2 cm of it projecting from the block/brickwork. I think since restraint straps are bent (cranked) around the block and bedded in the mortar as the wall is built up, replacing it is difficult and messy. If you can get a replacement strap, cut off the cranked end and align the new strap (minus the cranked end) laid end to end with the existing strap, refasten to the ceiling joists, then use the cut piece of the cranked end as a splice plate. Bolt through the holes in the existing strap and the newly installed strap using as many short bolts as you can get into what's left of the existing strap end where it protrudes from the gable wall. It's not perfect but you should get the lateral restraint needed to make the old strap viable again.

Yes you can retro fit restraint straps. Most builders merchants can supply them. Catnic make galvanised straps which can be nailed to the trusses (best to span at least 3) then they can be screwed or bolted into the brickwork