Thanks for the advice, The cake is stacked with dowels and carboard cake bases.
There is a dowel running through the centre of the first three tiers and four dowels on each tier supporting the cakes, the boards are stuck to each tier with royal icing, and the cakes are stuck to the board with a thin layer of royal icing.
I will take my husband with me to transport the cake and will use rubber matting on the floor of the car with the cake in a bread crate and more rubber matting underneath it.
One good thing is the venue is 6 miles away and the road goes straight to the venue with no turning off.
Thanks for the advice about a repair kit. I did make extra decorations in case i needed them, but never thought about taking them and stuff i need to use if their is a problem.
I really do appriciate all of your advice,