Two quick points - what about reducing our meat consumption? Not asking people to cut it out completely, but cut it down. Make meat a weekly treat (there's the marketing slogan, right there, free for anyone who wants it!)
And about plane travel - the problem isn't with the people who fly for a few hours on a vacation once a year. The problem is with people who attend an event like COP26 and instead of a 4 hour train journey, take a private jet. And then use that private jet to fly back to London for a dinner engagement. Yes PM Bobo Johnson, I'm talking about you. And the people who call for everyone to live greener and more environmentally friendly lives, yet have 26 gigantic properties, and fly everywhere by private helicopter and private jet. Prince Charlie, take a bow, I'm talking about you. Maybe we need a system where we all have a flight mile allowance per year. That doesn't punish the little people, only the overusers.
Let's subsidise smaller and/or electric cars. Let's give vouchers for every citizen to get a free bike. We need carrots, not sticks. No-one wants to go backwards into a smaller, lesser life, unless we can see some benefits waiting for us there too.