UK resident with US income

I am currently a US permanent resident (Singapore national) who will be moving to the UK to take up residency shortly. I intend to relinquish my US residency. I will be self-employed in the UK but all of my self-employed income will come from US employees. I am presuming that I will be receiving 1099s from my US employees. Will I be paying taxes in the UK or the US or both? And what about Singapore?

Whether you are employed or self-employed the income will be subject to UK tax and NIC; albeit potentially subject to overseas workday relief if you are employed.

If you have a green card, you may find these links helpful:

http://www.irs.gov/Individuals/International-Taxpayers/Taxation-of-Resident-Aliens

http://www.irs.gov/Individuals/International-Taxpayers/Determining-Alien-Tax-Status