You have to file US tax forms, but it's not likely you will owe any tax. US citizens are taxed on their worldwide income. You are allowed to offset your overseas income from your job with the Foreign Earned Income Exclusion (Form 2555, up to $80,000 is excluded), you can offset your taxes with the Foreign Tax Credit (Form 1116), and the US/UK Treaty can also be used here and there to reduce your taxable income (particularly certain pension clauses).
Even if you earned no money, you may have a filing requirement for a Foreign Bank and Securities Accounts Report (Form TD F 90-22.1). You must file this form each year you:
a) Have assets in foreign bank(s) that exceeded $10,000, including joint accounts.
b) Have signature authority over another person's (or company's) bank account that was in excess of the $10,000 limit. These accounts could include:
i) minors,
ii) elderly relatives,
iii) your employer's accounts, and
iv) charity or church accounts.