It is important for you to know that there are no sources of funding available to overseas students once you are in the UK. The UKCISA website www.ukcisa.org.uk/ contains a section on sources of funding. Most sponsors require you to apply from within your home country. An application for a visa extension would be refused if the Home Office felt that you did not have enough money to continue to support yourself in the UK.
If you are from a Commonwealth country (other than the UK), you may be able to access funding from the Commonwealth Scholarship Commission or All Saints Educational Trust (ASET). Please visit their websites for further information (links on the right).