Originally Posted by J.JsOH

The date to file US tax can be extended out up to 6 months beyond the April 15 Tax Filing deadline.

This then gives you time to file your UK tax before you have to file the US return.
Sure, you have to scramble a bit to get the UK filing in quite early and you don't get to use the full period (that a non-US person would get) to file a UK return but there is sufficient overlap to achieve both within the US (extended) deadline.

By living (as an American) overseas there is a two months automatic extension of filing US return. This can then be extended (probably necessarily) a further 4 months by sending in Form 4868. http://www.irs.gov/pub/irs-pdf/f4868.pdf
There is a box to tick if you live overseas.
There is other useful info on the form about filing and paying.

But Note.....You must pay any US tax by the April due date or incur penalties.
There is no extension on the US pay-by April date.

Originally Posted by J.JsOH

ps @ SadinStates: Did you pay state tax in US ? if so then you probably have to file State tax for the part of the year that you lived there before you left and notify them that you have moved out of state.