My father left his house to me and my siblings but his wife can stay there till she dies. She and my dad only ever lived downstairs and rented the rest of the house out. Are we entitled to the rents? And since his death she has been with holding my mail that I have always had sent there although I don't live there? What can I do? Can I move in legally?

It depends on the specific wording of the document that spells out the details of this residential trust. If it says that something like she has "'sole and exclusive use to occupy and enjoy as her residence until her death" then she can pretty much do awhat she wants - including renting out the upper floor - as long as she abides by whatever conditions may be set (for example, she may have to pay for insurance, property taxes, utilities, and maintain the house in good repair). I suggest that the executor talk with an attorney (whoever is helping with probate) to make sure the terms and your rights are clearly understood.

As for holding your mail - when you go to collect it does she refuse to give it to you? She cannot destroy your mail, but she she has no obligation to be your secretary, so obviously you need to have mail sent to your own residence, not your step-mother's.

It just says that she can reside there for as long as she wants as long as it is her main resident and she pays the taxes etc, it doesn't state she has sole residency?

It says if my wife is living in the house at the time of my death as her main residents then my trustee shall allow her to reside in the house free of rent so long as she may wish but so long as she pays all the rates taxes and other out going in respect of the house. She can use all effects ( furniture etc. In connection with it but can not sell the house or the effects without her written consent?

And also I'm the excecutor of the will and my address is listed as the house we are talking about? No doesn't say Sole or Exclusive.

Again, you probably want to consult with an attorney. But I bet the intent was that she would have exclusive use since no other family members were living there at the time of your father's death.