Hi
We have just returned from our 3 week jaunt to France and used Eurotunnel- We arrived at the terminal at midnight and slept in the van in the terminal car park no problem. A nice lady even comes and wakes you up when it is time for you to queue for your train. They don't seem to have any problems with you staying at the terminal and it is not as noisey as you would think as the caravan parking is at the other side of the main car park.
Caroline