Unmarried partner visa- Immigrations mistake

[Carolina]

I'm Argentinian currently living in England as a student and my boyfriend is British. We have been togheter for almost 3 years but only continuously living since July 2004. We want to apply for an unmarried partner visa but we are not sure of the meaning of "2 years akin of marriage". Does it have to be exactly two years living together constinuously or permanently? All the times I came to England and he traveled to Argentina (getting into both countries as visitors) or we traveled together.. Can they be considered part of that two years?! What evidence can be submitted if we don't have joint bank accounts and e.g. council tax doesn't show that we've been together for 3 years?! Family letters?! Passports?! Any ideas?! Hope someone can help!!!!

In addition to the doubts about an unmarried partner visa at the moment I'm waiting for a response from immigrations as when I applied for my student visa in Croydon ones I got to England as a prospective student the gave me a Resident Permit (with the limitations of a student visa) until 31st of december 2007. On the papers I submitted it was clear that I was only going to do my last year of uni in England and that my studies finish in Oct 2005. I called immigrations to check about my work situation with that visa and they told me that I only have 4 months since I finish and that it doesn't matter what my visa says. So basically.... they said I can only stay until september!!!!
The enquiry to immigration about my current situation was made a month ago and we only got a standard letter saying they were dealing with the complain and to we send a fax to check go it is going. We already sent faxes but we don't get any response! What can we do?! Can they say that they made a mistake but that it doesn't matter and I have to leave now?! Can they come back to me saying I have to leave in a week or so?! Have anyone been in a similar situation or knows about it?!
Please, I just don't know what to do and trying to talk to immigrations is like trying to communicate with a wall!!!!!!!!!!!