Cancelling your accommodation
There is no provision for a legal cooling-off period for holiday and accommodation bookings. You are bound as soon as you have confirmed the booking. The accommodation providers themselves decide whether (free) cancellations are acceptable. This will be stipulated in the cancellation clause.
Have you made a separate booking for a plane ticket, which is then cancelled? You can only cancel the accommodation booking if the general terms and conditions of the rental agreement include a relevant provision.
Does the contract not give the option to cancel, not even subject to cancellation charges? In that case you will have to pay the full amount of the rental. You may be able to claim it back if you took out travel insurance.