It's like they're just putting their heads in the sand. Meanwhile people are dying, hauliers are being threatened, holiday makers having trips ruined.
I'd do the following:
Make clear any illegal entries will be turned back to France. Make clear there are not limitless jobs, housing etc in the UK. Make clear no benefits to new migrants (if this isn't the case then change the law).
Presumably the migrants think the UK has lots of money and opportunities, otherwise they wouldn't be risking their lives to leave France (a safe country).