Hiya
I'm from LA and live in Bristol. I had a similar situation and used the following near the British consulate in LA. They were really helpful.
I overstayed a visa by a year. Had returned with a six month visa and during that time got a work permit. When. I got married I didn't want to have any issues, so hired A Briggs.
Good luck.
http://www.abriggs.com/locations/LosAngeles/los_angeles_passports.php
A Briggs are not qualified immigration advisers, nor are they lawyers (and agencies like them have been known to give very bad visa advice in the past, which would have resulted in a visa refusal if their advice had been taken).
All they can do is take a look at your docs to check nothing is missing (like your passport) and then submit your application to the consulate in person for you... So you are really just paying for a glorified delivery service.
Plus, the LA consulate no longer processes visas - all visa applications are sent to NYC now, and family visa applications are redirected to Sheffield from there for processing, so contacting an agency in LA isn't going to help, because they aren't anywhere near the NYC consulate to submit the application. Also, visa expediting agencies aren't really worth the extra money anymore as UKBA no longer allows them to get faster processing, so even if you pay for their services you won't get your visa any faster than just mailing it yourself. If you want faster processing, you'll have to pay $300 for the UKBA priority processing service (15 working days) on top of the visa fee and any agency or lawyer fees.
Here on the forum we would usually recommend someone like Laura Devine as a good immigration lawyer, who I believe has offices in NYC.