If you're not French (or don't have a French partner) then you need a compelling reason. Tourism or business is not a 'compelling reason'.
I'd expect them to be wise to people arriving from alternative routes (e.g. Netherlands and then Switzerland). Especially if you're using a UK passport.
If you're trying to sneak into France from Great Britain, there must be a people trafficker looking for a back load on his otherwise empty RIB who would be glad of a free £20
Thank you - flights now changed...