In reply to Dark-Cloud:
You've probably already looked this up, but this site sets out the current requirements on entry. The UK and Switzerland are both on the Green list:
https://www.interieur.gouv.fr/covid-19-international-travel
You still need to present a vaccination certificate, or if you don't have that, a negative Covid test certificate. You can get a fit to travel antigen test with a travel certificate done for around £15-30, so if you are at all concerned it's not a massive deal to sort out. If you've been fully vaccinated, it takes about 5 minutes to generate a vaccine certificate for travel from the NHS app.
The sworn declaration isn't needed anymore.
As I said before though, it's highly unlikely you'll be checked when entering France by road.
However, you do still need to be fully vaccinated to enter Switzerland. I understand this requirement will be dropped from 2nd May. This Swiss Govt website is the primary source of information on the current rules https://www.eda.admin.ch/countries/united-kingdom/en/home/representations/e...
The UK Govt FCO travel advice site is absolutely useless, and very confusing, so don't bother with that.
Post edited at 22:41