In the sample shown below, there is no Rehab centre but all the other facilities you need are in there. I usually fire my stars when their addictions get out of hand anyway. If you are playing in Sandbox mode then you may not need some of the facilities, e.g. the Laboratory, if you have already researched everything in Tycoon game mode.
There is space for seven of the largest trailers plus room for quite a number of ornaments around them. To keep things clear, I haven't shown any ornaments anywhere in the studio, except for some cars in the front parking lot.
Also not included are canteens or sanitation facilities, but you can see some small left over bits of space scattered throughout the studio that can be used for these.
The arrangement attempts to minimize travel distance. The Casting Office is in the center so crews will head out to the particular 'region' they are shooting in. So long as your movie shoots most scenes within one genre, e.g. Sci-Fi, then all the sets they need are in close proximity. The general-purpose Travelling Automobile and Stage sets are centrally located.
If you download some additional sets from Lionhead's PropShop, you can create some room by ditching the seventh star trailer, or getting rid of the Laboratory if you've already researched everything.