Personal insurance

my stepson (22) has severe autism , severe learning difficulties and is none verbal. We have had insurance cover for him for when he goes to carers houses for his respite. After 3 years we’ve had to make our first claim as he used too much toilet paper and flooded the bathroom causing over £2500 worth of damage to the floor, walls and ceilings of the room below. We’ve contacted the insurers believing this be covered but they only cover up to £1000 and £50,000 public liability for which this isn’t. My question is, are there insurance companies who over personal insurance for him when he’s at other people houses including friends and carers who offer more than a £1000 ? We only get 2 nights respite a month as it is and if we lose the people we’ve grown to trust with our son I’m not sure what we’ll do , thanks for any info