I always stick to the old familiar Dover-Calais and had no problems last June, when it was all kicking off. Nice and peaceful, not a worry.
That said, March before last, a friend went Portsmouth-Le Harve and reckoned it was much better. Avoided London if you're coming from the West of the country, apparently (i don't know how) he said it avoided Paris and he said it was a much nicer drive. I've not done it but it's worth a thought.