As most environmentalists have argued. This isn’t about the family holiday to Rome once a year.
This is about the 15% of people who account for 70% of flights.
As a side note, and not diminishing the wonderful culture I’ve been lucky enough to experience across Europe before our current prolonged act of national reputational self harm began; if we were in any way serious about support for rural and coastal communities in the UK whose tourism industries have been under huge pressure in recent years, we might consider investing in electric hire vehicle hubs at the ends of some rural rail lines (in Scotland, Cornwall, Dorset, Wales, for example) and consider the pricing structure for leisure journeys so again, people have a more straight forward route to a much greener holiday than the cheaper options to more distant destinations the low cost airlines currently offer.
Perhaps some form of national railcard / loyalty card scheme with a reasonable reward for an achievable spend ?
£30 a year railcard.
Integrated into a nationally accepted ITSO smartcard
X% discount off off peak fares.
Spend £X in any calendar year on your smartcard and receive a voucher to allow return off peak travel between any 2 stations in the UK for £50 adults, £25 kids (voucher valid for 2 adults and 4 kids).
I raise this here, as this is exactly the kind of thing airlines have been doing for years, with huge success ...