Unmarried partner - time spent living together

[Roger734]

Hi there, first post but I hope someone may steer me in the right direction.

Quick background:
My visa: Tier 1 Extension from HSMP (NZer)
My gf visa: Tier 2, currently working (NZer)

As of May next year my gf and I will have been together for more than 2 years. By then we will have been living together for 18 months. I regularly went to stay with her for 2-4 nights per week in London for at least 6 months before we started living together. She was working there on her WH visa and I started a business in Oxford so had to live here.

Is it possible for me to apply for an unmarried partner (dependant) visa in May based on my Tier 1? The guidelines say living together for 2 years with living separation of up to 6 months. Am I able to claim the first 6 months as living apart due to employment? I have all my old bus tickets to London (dated) and cellphone records. I can also get affidavits if they are worth anything.

She is on a Tier 2 at the moment so I assume that if it were possible she could switch without leaving the country?

Any help would be greatly appreciated.
Roger