Travellers to The Philippines need to arrange comprehensive travel insurance before visiting the country, because there is no reciprocal healthcare agreement in place between the UK and the country.
Outside the capital city, Manila, hospitals in The Philippines are not of a high standard, and more severe conditions will require medical extraction back to the UK (costing around $100,00). You should make sure that you insurance covers this.
Malaria and Dengue Fever are a problem throughout the country, and you should consult a doctor prior to travel in order to arrange appropriate protection.