5 Million shouldn't cost that much more. About time people woke up in this industry regarding risk. 1 million pound wouldn't even cover you for domestics.
Its not the cost of damage you need to think about but the rediculous fees the lawyers charge.
If someone tripped over your hoses and you hadn't posted adequate warning signs they could be unable to work for the rest of their lives. That claim could be well in excess of a million pounds.