Think it’s 45 minutes crossing.
Total time depends on how busy a day/time you’re travelling. You’ll get an email from tunnel peeps a few weeks before you travel saying whether you’re scheduled on a busy time or not. If one of your days is a busy one, there’s not much point turning up early. Just plan on turning up when they tell you (I think it’s minimum of thirty or forty minutes before departure). You drive up, the ANPR system recognises your plate and you’re given options on the screen for when you want to depart – if it’s a quiet time, you may get an earlier option. If it’s a busy day, you’ll most likely the one you’ve pre-booked.
So all in all, if you time it well, it could be around an hour and a half between turning up and being on the road in France. Transport links at either end are excellent, especially in France…you’re straight on the autoroute in a few minutes.