Easyjet offer flights from Gatwick to Bordeaux regularly in the summer months. These are available to book now. The drive from Bordeaux to Monflanquin is about 1h45min.
Flying into Bergerac Airport is another option, as Bergerac is slightly closer (40min to Monflanquin). Flights operate from London City airport (BA - released early September), and potentially from Stansted with Ryanair.
Driving from St Malo is what we will be doing, and is another option if you don't mind a road trip (6h30m). DFDS sail from Jersey, with bookings likely opening in March 2026. However if you choose this option, don't wait this long to book your accommodation as places can get booked up quickly, especially in a small town like Monflanquin!