It shouldn't be necessary for you to blow big $$$ on an immigration lawyer since you have a pretty straight-forward situation. And since you live in the UK, you should be able to file your paperwork through the London Consulate with little or no problem.
https://uk.usembassy.gov/embassy-co...0.2003709640.1501102481-1746197672.1499264171
Cheers,
Bev
https://uk.usembassy.gov/embassy-co...0.2003709640.1501102481-1746197672.1499264171
Cheers,
Bev