You have FAR bigger problems than this trip to France:
He gambles and has lost loads of money
You bailed him out, to your own disadvantage
He flirts with other women
You don't do anything together as a couple
He's financially abusive - who the FUCK gets to live on £400 spends a month?
He makes all the decisions and you just do what you're told (such as you're only getting £400 and you just accept that)
You pay for everything
He's secretive and hiding things from you
And I bet there's more. I bet you do most of the housework too, most of the cooking, shopping, cleaning etc
I mean, the trip to France might be the straw that broke the camels back, but fucking hell, all the rest of it is grim. You've been with him 34 years, iirc? Okay, sunk costs fallacy may be at play here, but honestly, having left a long marriage myself (20 years), I would get away from him and start over. You deserve so much more than this. And fwiw, I don't think for one second his trip to France was to chill out for a few days. There will be a reason it was France, and you'll never know what it was, because he's an absolute bell end who takes you for a fool. He's been secretly planning this trip, and you had no idea. Two separate lives really. What's the point of him?
I would get your finances in order, get your Solicitor to draw up a separation agreement laying out all the finances. A few things to think about : if his pension is bigger than yours, you can be financially compensated for that. If your career took a back seat to his, for raising children, you can be financially compensated for that too. I'd take him to the cleaners. How DARE he treat you like this!