Openreach Engineers are covered by Accidental Damage through Openreach. Although that doesn’t mean they’ll drill holes here there and everywhere without facing repercussions if they’re caught drilling holes without using a Mains Detector and or Drilling out even though the Detector showed something may be there.
As for Contractors that’s a different story. I can’t speak for Morrisons but I know Quinn’s and Kelly’s guys, although they work for Quinn’s/Kelly’s they’re in fact Self Employed so are responsible for having their own Damage Liability Insurance.
I can understand you assuring them there’s nothing there but are you going to assure them you won’t peruse a damage claim if they did drill through a water pipe, electric cable, etc?
