Not MS, cavity wall insulation?

Hi all

Can anyone please help? I have asked about this before , but a different question.

Has anyone had the cavity wall insulation done with the polystyrene balls? We had a man from British Gas come and do a survey and he confirmed that my Landlady would get it done free of charge, but they only use the mineral wool type of insulation and apparently that is no good for this property so we need to find a company that uses the polystyrene balls

Thanks