Yes, they had the big bowl-shaped screen in Studio A, which they used for the school bus and anything else they needed it for. It was originally built for UFO Kidnapped. When I was there, they also used it to do the "weightless" effect in my "Outer Space" episode and the jungle scenes in my "Wildlife & Animals" episode.
There was also a smaller Chromakey setup that they used for little things like the green slime cloud floating around the space shuttle in "Outer Space." The control panel of the shuttle was actually a spare Chromakey console, and they ran a live video feed into it so that Alasdair and Adam could see where the cloud was supposed to be.
Of course, if you'd listened to my interview on "The Space Show," you'd already know that.