proof for unmarried partner visa

[virus10]

Hi, my partner is due to attend his interview for an unmarried partner visa next week, which we are both nervous about, we have tried to find all the proof we could to show we are a couple and have been living together for 2 years.
The thing is, he had to go to NZ to apply, so he has been there since January this year. The oldest bit of mail I have is from March 2005 ( Ishred everything) BUT we actually moved in together Dec 2004, so does that mean that the 2 year period must start from the date on that bit of mail? Making 2 years - march 2007? If so, will the fact that he has been in NZ sorting out this visa since January make it only 1 year and 10 months? It is still our room, all our belongings are here, we are paying rent and bills here still, and we will continue living here when he returns.
This sound confusing on re-reading it but any replies from anybody with knowledge in this would be much appreciated....