I am not a tax attorney, nor do I play one on TV, however because my DH and I live in an area with LOTS of US expats, this is my understanding.
The US gov't allows you to file for an extension in order to reach the 330 day requirement for foreign exclusions/credits. I've read that they automatically extend until June 1 (or 30th, can't remember which) if you have a foreign address, but IMHO I would file for the extension to Aug just to be on the safe side. This advice only applies if you intend on staying outside of the US for 330+ days (e.g. if you were to leave the UK in April for some reason, you would never qualify for the foreign income exclusion anyway, so ignore everything I just said)
NOTE: This is not an extension to pay (if you were to be in a situation where you would owe taxes) but rather an extension to file. Normal disclaimers apply.
My DH moved to the UK in June 2008, so our plans are to file for an extension and then file for "real" in July. Downside - we don't get our expected Federal or State refunds until then.
There must be some advice out there for tallying foreign income and taxes paid for non-coincident tax years, so I would probably google search for that.
BTW, DH and I use TurboTax too... and I experimented with different dates (i.e. go ahead and enter data as if you had completed your 330 day requirement) to see what impact that will have.
Good luck!
Edited to add: Here is the IRS website with info on the foreign income exclusion and links to the various forms you might need:
http://www.irs.gov/businesses/small/international/article/0,,id=97130,00.htmlAnd here is IRS Publication 54 directed specifically at helping folks who live and work abroad with their tax questions:
http://www.irs.gov/publications/p54/index.html