Spousal Visa - Accomodation

Me and my fiancee (soon to be married) will be applying for our Spousal visa in the near future.

I have a question regarding Accomodation and there requirements.

We plan on staying in my familys house (Mother and Brother living here too). Now the house is very well sized and plenty large enough for the 4 of us to live in. I do pay rent to my mother every month. Will they see this as acceptable accomodation? We will certainly not require any form of handouts/benefits from the government and will not cost them any money whatsoever. What sort of proof would we need to give to tell them about this arrangement?

If all goes pear shaped, I earn in excess of £23,00 a year, so could move out if need by, but really is a last last resort given the current economical climate.