sorry i keep using IDL, i did mean IDP, i think because i keep remembering it from the scams it was used in
not sure if you need a IDP for the UK, but there is a good reason to get one, if your stopped by the police, good chance they will not know what a driving license from the philippines looks like, but they probably would know what a IDP looks like, as it's an internationally recognized form of identification, carrying your name, photo and driver information.
and if you are stopped, they will probably want to see your passport and see when you first entered the UK.
also http://www.aaphilippines.org/news_view.aspx?newsID=34#3
and it only cost 300php