There have been whole email threads on fan lists discussing the existence or otherwise of a “Lobby” between the Police Box and the inner console room doors.
There are actually many Dr Who serials in which the inner doors open and we see straight out onto the scene outside the Tardis at which point we are very clearly not looking through a police box. There are also serials where, beyond the inner doors, is either a completely white or completely black void. This void could be interpreted as a lobby, with the supposition that there are actually two pairs of doors and a lobby in between. However the doors get discussed in the dialogue a lot and there has never been any suggestion at all that there are inner and outer doors…
My Tardis has to exist without the benefit of transcendental dimensions, relative dimension stabilizers or any such technology, so my Tardis has a Lobby. It’s matt black, has 12 inch roundels and joins the back of the policebox through the doorway to the real room and then opens out to meet the console room doors, which are set at an angle across the corner of the real room to accommodate the dimension change. Like this:
I’ve made the lobby dark inside (by painting it matt black) both to enhance the separation from the outer world you feel inside the console room, and also to increase the visual impact of entering the brightly lit console room from outside. This works particularly well at night.