There's no legal definition of an 'hotel' in this country, so there are no separate rules for 'hotels' than there are for other types of holiday accommodation, such as the chalets at Center Parcs, B&Bs, or self-catering accommodation. i.e. nobody has ever created a law which SPECIFICALLY states that an hotel must have staff permanently on duty. (Many small hotels/guesthouses/b&bs are run by just one person. It would be ridiculous to state that they could never go shopping or visit the pub if a guest was present in their property!).
All that applies is the same general 'duty of care' that applies whenever someone provides good or services. As long as, for example, they've installed and maintained adequate fire alarms, together with ensuring that all fire exits are clearly lit, signed and freely accessible, they will have discharged their duty in respect of fire safety.
Chris