Using batts around reveals when the rest is PIR

[BarnabyT]

I am closing the cavities on a side extension im having built. Standard cavity wall construction with 100mm cavity with 50mm PIR and dense concrete blocks. I've noticed that around some of the reveals the insulation is missing. Not an ideal situation and I cant just slip in PIR boards due to the wall ties. Would it be acceptable to fill the gaps with 100mm cavity batts? I know its not ideal and no doubt comments will be made about sloppy standards etc..... but nevertheless, I just need a practical solution at this point. I assume it won't cause any issues ......