As suggested above, get rid of that pair asap , before you require the services of Dominic Littlewood & Melinda Messenger .
I was about to suggest that too , if it wasn't for the serious risk to your property , it might be entertaining to get the TV crew in to capture them at work .
Did you catch the names of the two 'workers' , wasn't Stan and Ollie by any chance ?
More seriously , I'd contact the 'reputable' company who have subcontracted this lot and complain to them , focussing primarily on H&S but also on competency and workmanship .