Thanks for all responses, its going to be a tough one, letting them out in the morning would be ideal, but if they didn't show up before I had to leave for work, I don't know what I'd do. I think I may have to wait until I move, and get a place with a back garden that i can cat proof. Cars are the biggest danger for me, and that they might get scared and dart to somewhere they don't know. Its all very scary, as its the first kitten I've ever owned that's not already experienced the great outdoors.
And given that she's a Mau, she's quite stealable.
I want to give her the freedom that my other cats experienced, but i dont think now is the right time, not sure.