I obviously don't know what is going on with these machines at LHR overall, but they sure are pretty popular with airports and elsewhere around the world. LAX even uses them to check satisfaction with their bathrooms..
From
https://www.cnbc.com/2019/05/31/lax-...isfaction.html
"HappyOrNot says it now has 30,000 terminals in 130 countries, with over one billion button pushes to date."
"At some terminals here, monitors have been placed at bathroom exits where passengers can press a happy face or unhappy face to register their feelings about the bathroom. Press the red “unhappy face,” and you’re presented with a list — does the bathroom need more toilet paper? Paper towels? LAX is using this real time feedback to stay on top of keeping bathrooms clean (and they say the happy face monitors are also regularly cleaned)."