I tore out the cupboards until I came across the perfect instrument... A pasta bowl!
This Tupperware bowl fits underneath a colander and the snap on lid keeps the pasta warm (a ridiculously good invention!) The beauty of it is it's so big, the dome is huge so it doesn't touch the cake below.
Be careful using Tupperware, snapping the lid onto the bowl- it's a spring action technique that is supposed to be done when the bowl is standing upright so it's a little fiddly when there's weight on the lid.
Have a root around your kitchen some day when you have time on your hands and figure out what container is the best for transporting a cake- so when all the hard work of baking and decorating is done you don't have to panic over how what to store it in!