I am a US permanent resident but I am a Filipino citizen. I am planning to travel to the Philippines and wanted to get a ticket with a 15 hours layover in the UK. Am I allowed to go out of the airport and have a tour to London?
You can transit without visa (TWOV) landside (i.e., you are allowed to leave the airport). Citizens of Philippines can TWOV.
A visa national who is going to the UK simply to travel on to another country may enter without a visa if these conditions are met:
- They arrive and depart by air
- Their onward flight is confirmed and departs within 24 hours
- They are properly documented for their destination and have a visa if they need one
It is a good idea, however, to have some supporting documents (e.g. work contract) available, be dressed reasonably well etc., because TWOV is a concession.
The concession is operated at the border where you arrive in the UK and is at the discretion of Border Force officers. You may not be permitted to benefit from this concession and may be refused entry to the UK.
The quick answer is no without a visa. As a Philippines national you need a visa to go through the uk border.
This is clearly explained by the uk border agency here http://www.ukba.homeoffice.gov.uk/visas-immigration/transitthroughtheuk/visa-to-transit-landside/
Check the "Are you a visa national" section under "more information"