There is some excellent UK government advice here on how to choose a tax adviser:
http://www.ccab.org.uk/ChoosingAccountantTaxAdviser.php More broadly, for most UK based individuals there are considerable advantages in having US tax returns prepared in the UK.
These include:
1. The client and the adviser being located in the same time zone.
2. Client documents and workpapers being held outside of the United States; which many people perceive as providing additional protection in the event of IRS investigations.
3. Advisers outside of the European Union are unable to offer the protections to clients provided by the Third European Money Laundering Directive, which requires all tax professionals throughout the EU to be regulated and supervised for anti-money laundering protection purposes. Here in the UK it is a criminal offence to offer tax advice unless the adviser is supervised. Quite unlike within the EU, there is no requirement for mandatory regulation of tax advisers in most of the United States.
5. The fact that although there are roughly one million paid tax professionals within the United States, that there are naturally only very few amongst these who understand enough about the US reporting of UK based income and assets.
4. The ability in the unlikely event that things ever go wrong to get issues addressed through a supervisory body that is closer to the client than an adviser located several thousand miles away.
