My fiancée and I are in the process of an I-129F too. Fun, huh?!
While the official website says the process can take anywhere from 6-12 months for the visa to be issued, it is moving along a bit quicker for us. If you want to know the details, check out my post under "Visas" and the Message "American vs. British Fiancee/Spousal Visas."
The only "copy" I sent in was my birth certificate. It was not notarized. They accepted our petition. I am not sure about other copies you are sending in {if you have children or divorces involved} so someone else here will able to help you on that one hopefully.
I am not sure how long your process will take; it all depends on your circumstances.... We do not have children, have never been married, do not have any police records, etc. Also, my fiancée has a SS# from working here in America for 1 year so maybe that's a bit of a help on our side.
On the official website, it says you can ask how long your process will take in a covering letter. We asked in our cover letter and of course, did not get a response.
Your statement of intent: We sent in a one page statement of our intent to marry, our plans to marry, where we would live, etc. In other words, a lot of mumbo jumbo.... Again, they accepted our case. We did not {and still don't} have an official person marrying us yet.
Check into the website of where you must file-- it will give details whether or not you can do it in person. Our location to file {I live in NY} was VT. We sent our package in and got a receipt of acknowledgment that they received our package and money order.
You can call the National Customer Service Call Center {from the US}: 1800 375 5283 and ask the questions about filing in person, a letter from the priest, etc. We called twice and had a list of Q's written prior to the call. Plan on waiting at least 30 minutes for someone to answer your call. {If you're in the UK-- maybe someone here can call on your behalf??}
And again-- I have details about the process we are in under the "visa" section if you want to take a look.
These sights have helped me:
http://travel.state.gov/visa/immigrants_types_marriage2.html#1dAnd once the paper work is done on this side, it will be forwarded to the UK-- we are going thru the American Embassy in London:
http://www.usembassy.org.uk/cons_web/visa/iv/fiance.htmBest wishes and keep us up to date with your journey. The people here have been a great help with info and support.
edit: spelling