If your pet had a first rabies vaccination at the six-week mark, the 21-day waiting period clears around now, which is worth double-checking against the actual vaccination date rather than assuming it's exactly 21 days from when you booked the appointment.
This is also the point to lock in transport if you haven't already — add your pet to a Eurotunnel Le Shuttle booking, confirm a ferry operator's current pet policy, or check an airline's cabin pet allocation, all of which can fill up closer to travel. If you're flying, confirm your airline and arrival airport accept pets at all.
Confirm pet-friendly accommodation is actually booked and the pet policy is in writing, not just assumed from a listing's general description — message a Gîtes de France property, Airbnb host, or hotel directly if the listing doesn't spell out fees and restrictions clearly.