MAM,
As SWMBO doesn't do boats, I have to use the tunnel & always take the late night crossing.
As Olivier says, once you get off the other side, you get a clear run with hardly any traffic, whichever way your heading.
I usually drive untill I start feeling tired then stop at an Aire & get my head down for a few hours before going on.
Whist I agree that you don't get a decent break as you would with the ferries, this is ofset by the time saved.
Unlike Euro, I personally have never experienced rudeness by any of the staff at Eurotunell, in fact quite the opposite.
As for waiting to use the loo on the train, why bother with it, apart from the fact that they're at either end of the train, and it's a long hike through the carriages if you're in the middle, you have a perfectly good one in your caravan or motor home!
All I can say, athough I'd prefer to use a ferry (cost saving of usually