DCF I-130 Filed In London
DCF is the usual US immigration option when a married US/foreign couple live outside the US and want to move to the US. When the immigrating spouse arrives with his/her Immigrant Visa, they become a US Permanent Resident at admission and are issued a 'green card' to live and work in the US.
 UPDATE: Sep 1st 2013 DS-260 replaces DS-230 Parts I and II - For London Based Applicants
Please note that as of 1 September 2013 you are now required to fill in form DS-260. This replaces the paper form DS-230 Parts I and II.
You will need to submit the following according to http://london.usembassy.gov/ds2001.html
 UPDATE: August 15, 2011 "DCF" Ends August 15 2011
This will not directly affect people filing I-130 in London. This is about 'real' Direct Consular Filing, to a Consulate abroad. Filing to overseas USCIS offices will not change. If you are planning to file I-130 somewhere overseas, that is not London UK, please read this thread: http://britishexpats.com/forum/showthread.php?t=721270
 Residency Requirements
Filing the I-130 abroad may shorten the total immigration timeline. However, this option is only available to US citizens living abroad. The DHS office on London has set the requirement at six months minimum residence in the UK -- both legal leave to remain permanently and actual residence.
For US citizens resident in the United Kingdom, Immediate Relative petitions are filed by post at the DHS Overseas Office in London ("the Embassy"). Their requirements state:
"The DHS London Field Office has jurisdiction for adjudicating I-130 and I-360 petitions from U.S. citizens who have permission to reside AND who do principally reside in the United Kingdom. "
This is generally demonstrated with an Indefinite Leave to Remain (ILR) stamp and other evidence of your genuine residence in the UK.
 Application Overview
There are two steps to applying for the Immigrant Visa: filing the petition and applying for the visa when the petition is approved. Please research and understand what an Immigrant Visa is and make sure the applicant qualifies to immigrate to the US. Applicants with a criminal history, disqualifying medical condition or other visa ineligibility should consult with a US immigration attorney for specialized help.
Visa Application Phase
In London, these cases have historically taken five months from start to finish. While this can change at any time, 4-6 months is a good guideline; leave sufficient time for your application before planning your move.
 UPDATE APRIL 2011
(this message recently appeared on the US Embassy London website. it's unknown what the actual effect on processing times will be.)
Planning Ahead U.S. petitioners who are planning on filing for their foreign spouses/children for immigrant visas to relocate to the United States should file the Petition for Alien Relative (Form I-130) a minimum of ten (10) months prior to the date of the plan relocation.
 UPDATE AUGUST 2011
Timelines continue to be unpredictable as new filing regulations take place. If you plan on filing an I-130, you should allow a full 10+ months for the visa application (including petition approval) before the foreign applicant may move to the US. You should check timelines in the marriage based visa forum here to find out what's current.
 Considerations Before Applying
The US citizen's other important contribution to the application is the Affidavit of Support I-864. This document has several requirements that may not have occurred to you:
When a sponsor has clearly not maintained a domicile in the United States, he/she will need to re-establish a U.S. domicile in order for him/her to be a sponsor. The sponsor may make a number of steps to show that he/she considers the United States his/her principal place of residence. Examples of things he/she can do are given below:
If the sponsor establishes U.S. domicile, it is not necessary for the sponsor to go to the United States before the sponsored family members. However, the sponsored immigrant may not enter the United States before the sponsor returns to the United States to live. The sponsored immigrant must travel with the sponsor or after the sponsor has entered the United States
 I-864 Affidavit of Support From Overseas
In order to issue an Immigrant Visa, the applicant must present an Affidavit of Support from their US citizen petitioner, known on the I-864 as a Sponsor. The I-864 requires that the US citizen sponsor to be domiciled in the US and have income or assets that show the immigrant will not become a public charge. Income must continue after the move to the US (IE foreign employment income aka your UK job will usually not suffice). Your assets, and those of your spouse, CAN be used in lieu of income, or you may have employment in the US starting up. A Joint Sponsor may be the only solution for some families. Please read the I-864 and its full instructions carefully.
Domicile is a difficult area to describe and it is interpreted differently at each Consulate. Casual observation indicates that some Consular posts are easy-going about this, as long as you have a US address (perhaps a relative), a job offer, have filed your tax returns and are making obvious plans to move to the US. Recent reports are the the Consulates in London and Montreal have become far less easy-going and are asking for more evidence that the USC is really moving to the US, than in the past. Please make sure you are reading current personal accounts for up to date information.
These are some official sites discussing domicile and how to show your intent to return to the US:
In order to file an I-864 the sponsor or joint sponsor must be a resident of the United States. However, sponsors residing outside the United States are not automatically disqualified from being a sponsor if they are able to show that they are temporarily resident outside the United States. Joint sponsors must be resident in the United States to qualify.
Please read the entire Domicile section and not just these excerpts. While this is the law/policy, local Consular practice can vary. As of this writing, domicile has been a recent, hot topic and most advice is given from a conservative point of view.
If the sponsor is not domiciled in the United States, the sponsor can still sign and submit a Form I-864 so long as the sponsor satisfies the Department of State officer, immigration officer, or immigration judge, by a preponderance of the evidence, that the sponsor will establish a domicile in the United States on or before the date of the principal intending immigrant’s admission or adjustment of status.
In the case of a sponsor who comes to the United States intending to establish his or her principal residence in the United States at the same time as the principal intending immigrant’s arrival and application for admission at a port-of-entry, the sponsor shall be deemed to have established a domicile in the United States for purposes of this paragraph.
Download the current I-864 and Instructions. Read any Special Instructions on the Download Page
 London "DCF" How To
Instructions for filing in every country are different. For cases at the London Embassy/Consulate, the instructions are laid out fairly clearly in their website. The links here are organized in order of use but please feel free to click around the various FAQs in the rest of their site.
An immigrant visa is required of anyone who wishes to enter the United States to reside there permanently, whether or not that person plans to seek employment in the United States.
The spouse of a United States citizen is eligible for immigration in the immediate relative category. The first step in applying for the immigrant visa is for the U.S. citizen to file an immigrant visa petition, Form I-130, with the United States Citizenship and Immigration Services (USCIS) having jurisdiction over his/her place of residence.
BE SURE to select the correct checklist PDF download (spouse, parent, child, sibling) and see the photo specs download, and credit card billing form.
*You must follow the above instructions, specific to London.
Validity Period of the Visa: Immigrant and fiancé(e) visas are normally valid for travel to the United States for six months from the date on which they are issued.
Visa Issuance is Not Guaranteed: No assurance can be given in advance that a visa will be issued to you. Only after all your documents have been checked, your medical examination completed and you have been interviewed by a consular officer, can a decision be made regarding your eligibility to receive a visa. Therefore, you should not resign from your employment, sell your property, or make final travel plans until you receive a visa.
 Top Tips
A tip before leaving the country: As a matter of general advice: when the father of a child immigrates to the US, it is good practice to maintain very good records and back-up documentation of child support payments for the children not living with you.