Don’t read the Daily Mail and you’ll be fine.
I've never had trouble and have used the train every year for past three. The French have put up very large fencing (paid for by the UK!) which as you leave the terminal zone, feels like you're driving out of a prison...
What are chances we would encounter trouble on the Calais side? With asylum seekers/immigrants
If you can get the time off work this is an absolute epic deal.