Chary,
Most of the US/UK accountants are indeed in or near London. This is because the majority of people who need that work are also in or near London. However, most of the US/UK accountants have about 20 - 40% of their clients living in other locations, and have not ever met about 10% of them. You might want to go to London the first time to meet him or her, but after that, you'll find that most work can be done by fone, courier, fax, post, and email.
To protect yourself, send all original documents by courier or photocopy before sending - do not trust the post!