So we discovered mold behind some drywall during a small renovation here in the US and it's more extensive than we expected. Never dealt with this before and the number of companies offering mold remediation services is overwhelming. What should you actually be asking before letting anyone into your home for something like this?
The moisture source question is the one most companies dodge. Any outfit worth hiring will want to identify what's causing the mold before touching anything. If they jump straight to cleanup without investigating the source you're paying for a temporary fix at best.
That source identification point separates genuine remediation from cosmetic work. Professional mold remediation services that handle things properly contain the affected area during the job to prevent cross contamination, address the underlying moisture issue and verify the result with testing rather than just asking you to take their word for it. The difference in outcome between a thorough job and a surface level one only becomes obvious months later when one stays clean and the other doesn't. Worth understanding what the process should actually look like before making any calls. More detail on what proper remediation covers is here http://totalhomerescue.pro/mold-remediation .