Those who fail to book pay twice as much at Heathrow.
And 15 days in its short-stay facility over the summer is £893 compared with £214 in advance.
There are also mangrove tracts and seaweed plantations nearby, for those who are interested in such plant specimens.
Finally, Poloyagan Beach have rocky outcroppings and coral reefs so one should be careful in trekking them.
They said all prices were clearly displayed at the airport and on the website.
The Philippines, being a country archipelago of islands and seas, have naturally wonderful beaches, some of which are famous the world over.
An eight-day stay between July 29 and August 5 is £88 if you pay in advance but £395 if you just turn up.