Proof of Living Together for Partners visa - HELP Please

I wonder if you can help me,

I am a New Zealand Citizen. I am currently in the UK on a Working holiday Visa, due to end on the 2nd Oct 06. I have lived with my English partner for the entire length of my stay.

I would like to apply for an unmarried partner visa in person on the 2nd Oct, under the FLRM application.

My question is, for the first three weeks of my stay, I did not have a bank account, or any mail sent to me. I was staying with my partner and his mother in a rented flat. All bills and the tenancy agreement were in his mother's name.

Will an explanation of my situation from me and my partner, along with a letter from his mother, stating when I arrived, that I shared the room with my partner (it was a two bedroom flat - us in 1 room, her in the other), and that we contributed to rent and bills, suffice?

My fist bank statement arrived on the 22nd October, so I am fine for evidence after that date.

Many thanks in advance for any help you can offer, or even if you could point me in the right direction would be great!