Genorp,
1) How long are you moving to the UK? The length of time can affect your residence status here. They have two kinds of residents: Ordinary Residents and Resident Not Ordinarily Resident (RNOR). These can affect your UK taxation, where shorter is better than longer.
2) They also distinguish between resident and domicile; most Americans who move here retain their US domicile.
3) The one year residency requirement will be met in a rolling 365 day year, so you'll meet it in April 2007; of which you'll get a prorata 2/3rds amount for 2006. If you return to the US for more than 35 days within that rolling 365 day period, you'll have to wait until January 2008 to file so that you're here for one full calender year (2007). Again, you'll be allowed a prorata 2/3rds amount on your 2006 return.
4) That's just the US return, your state return can be filed at the normal time.
5) Don't forget to take a deduction for all your goods you might be giving to charities before you move. Your moving expenses will be a good-sized additional deduction which should further increase your US refund.
6) You may want to open special offshore bank accounts here, as they confer tax advantages to nondomiciled persons. They're easy to do, and fully integrated with the UK banking system. Any local UK bank branch can help, though if you're a high wage earner, I'd recommend Barclay's.
7) Many companies pay for your tax return preparation in your first year here. Do check to see if that's a company benefit, as the returns can be upwards of 50 pages in the year you move.