Polly, safety for yourself is always number one. Ekka is right, do what you can do. Doctors can save all lives, and my plumber has lots of CYA statements on his quotes saying he doesn't take responsibility for unmarked underground utilities.
If you make the HO aware of this at the start there should be a good repore throughout the job whatever happens.
Just identifying the dangerous situation and advising them the remove valuables etc is bettering a bd situation. Hope all goes well.
