Just like car insurance many companies apply an excess charge to any claims. This varies from company to company and some give you the option to pay a bit more have their uk backpacker travel insurance policy excess free.
If a child were to become ill, most travel insurance polices will only cover the child and one parent to stay in the resort to look after the child. Everyone else would either need to go back home as normal or fund the rest of the group to stay also.
Sometimes when on holiday something could occur that requires you to have legal advice, where an accident has occurred but no one accepts responsibility or for poor hospital or other treatment. See if the uk backpacker travel insurance policy you are about to buy, has legal protection or advice also.
There are some companies that only sell travel insurance, look through the options available here at Financebam. Their speciality in the subject of uk backpacker travel insurance may be just right for you.