Hello,
Taking into consderation all your questions....
I recently completed all my back taxes going back to 2002. I had to do this for my partner's Immigrant Visa back to the states.... I was horribly confused by the entire process and had no idea what forms to file when and to whom.
I basically ventured onto the HR block website and began filling in the questionnaire to prepare my taxes and ended up having a special tax professional assigned to my case. They completed ALL of the forms for me including the 1040 form, 1116 foreign tax credit form, and form 2555 foreign income exclusion. They also filled in forms that act as substitutes for W2's.
The only preparation needed is you have to give them the amount of income earned for that year in US dollars ( use currency conversion rate for the year in question ), amount of tax paid in US$ and GB£, and the head office's addresses of everywhere you were employed for that year.
Since I am freelance, I worked a number of different places so my return was quite detailed and the process cost me $200 per return.
It makes the entire process so easy and takes the stress off your shoulders.
I would seriously recommend HR Block to ALL USA citizens living in the UK AND earning money here, since we have to file every year no matter how much we make!
If anyone wants to be recommended to the lady who finished my taxes, just let me know and I'll put you into contact.
Michelle