When my mate takes his Clio to the Nurburgring race track in Germany, he has enough room for all his tools, a set of wheels, loads of spares and all of his and his missus's travelling gear with ease. And helmets too of course.
Doesn't beat our old race team van though, ex-BT workshop transit, that used to take 2 sets of tyres (with another 2 in the trailer), a full tool chest and a roaming one, jacks, gazebos, chairs, two 'doors' (it's a caterham so they aren't huge), a spare nose cone, a safe and God knows what else, and still have room for a stove for some bacon butties. Obviously the last item is the most important!