Official British Governmental Advice:
Falls from height
There have been a number of serious accidents, some fatal, involving British nationals falling from height, including from balconies.
Do not take unnecessary risks around balconies or other high places, particularly if you’re under the influence of drink or drugs. If you are staying in a room with a balcony, follow the safety advice at the hotel or apartment, and watch out for friends who may be at risk.
In some regions you may be fined or evicted from your hotel if you are found to be behaving irresponsibly around balconies. Your travel insurance may not cover you for incidents that take place on a balcony or if you were under the influence of drink or drugs when the incident happened.
https://www.gov.uk/foreign-travel-advice/spain/safety-and-security