I got an unmarried partner visa in October at the NY Consulate, despite being two months short on my evidence. However, it's important to point out that I had been living with my partner since late August 2001, but we simply did not have the written evidence such as utility bills going back that far. We only had them going back to December 2001.
Also, we used a solicitor, which I highly recommend if you can afford it and if there is anything the least bit non-straightforward about your application. Although I ended up going to the Consulate alone (my partner was busy singing an opera in Wales), my lawyer had prepared and reviewed all our evidence with me. He also coached me on how to speak to them, and probably most important, he wrote a covering letter which I presented with my application.
Here's what happened....
I went up to the window and said that I was making an Unmarried Partner settlement application. The entry-clearance officer said, "Do you have written documentation that you have been living together for two years?" After I answered "yes" with a bit of hesitation, he replied, "Are you certain?"
At that point I realized the guy was trying to be nice and save me the $455 (and the "official" refusal on my immigration record) if I wasn't going to qualify. 'Cause once they officially start the application you have to pay the fee whether you get the visa or not.
So I said to him, "OK, I don't have bills and such going back to October 2001, but let me show you what I do have." And I showed him: My solicitor's letter explaining the situation; the earliest mail that I had gotten at this address, which was in December; a letter that both of us had written in early November 2001, requesting to add me to the electric bill; and the elec. co's reply which referred to the date of our letter, thus proving we had indeed sent it on that date. I assured him that it would be no problem for me to come back in December and re-apply if it came to that.
He said he would have to take these letters into the back and ask the chief ECO if they would be acceptable. The two minutes he was gone seemed like an absolute eternity. When he came back he never said that the letters were OK; instead he just started entering everything into the computer for the formal application. He had a list he was going through for pieces of evidence, which I passed through the window one by one as he called for them.
In the end, he only looked at 5 utility bills to prove my address. But he looked at our financial evidence very carefully. He asked for 6 months of our bank statements, my resume, contracts from my partner's opera jobs (this is because she's self-employed), and our mortgage documents. He also quizzed me about my own savings and what I intended to do for work in the UK.
He did not look at anything else out of the huge mound of evidence I brought with me.
He then went in the back and made copies of everything.
When he returned, he ticked "ISSUE" on the bottom of the application form, signed it, stamped it, ran my passport through the machine, stuck everything in a big envelope which he threw in a little tray, and sent me over to the payment window, where I paid my $455 and was told to pick up my visa in an hour.
The whole process, from start to finish, took maybe 12 minutes. It could have been as little as 10.
Now, if I had not had a good immigration attorney, I would have waited the extra two months even though it would have been inconvenient. Keep in mind that if you apply for a settlement visa and you are refused, it will be next to impossible for you to enter the UK as a visitor, even if you legitimately intend to leave and can show them evidence of that. The settlement refusal will be recorded in the computer system and it will show when you arrive in the UK for a visit and they run your passport through the reader. Immigration officials tend to assume that anyone who was refused permission to settle in the UK, and subsequently tries to come as a visitor, is not going to leave.
I also would not have tried this if I were applying from inside the UK. As others have said, the Home Office has gotten very sticky about the exact timing of settlement-visa applications. It used to be that you could send your UP application three or four months early, and it would take them that long to process it (at least) and they would give you credit for the elapsed time. They're not doing that any more.
hth
Emily