Retaining bolts as per instructions are in place to safeguard the drum during delivery. All hotpoint washing machines and washer dryers come with these attached.
The fact that these weren't removed - you have affectively damaged the machine and its operation. Only way to remove them is to have a engineer to use a pliers to remove them off - they are in the region of 4 to 5 inches in length. They do not pretrude into the drum simply were holding the drum from moving.
Those that have sheered off are simply scouring the inside of you machine as they pretrude out from the drum internally even with those sheered off at the surface level.
I hope your model was the cheaper end range, as it likely that this machine is beyond repair and certainly you have invalidated the warranty.
Hotpoint Helpdesk Service Engineer, February 2010