In the summer Eurostar runs a direct service from London St Pancras to Avignon (84 Vaucluse, Provence PACA)!!
Calling at Ashford International you can travel direct to Avignon without changing trains or battling your way through Paris from Gare de Nord to the Gare de Lyon. The journey takes under 6 hours and runs 3 May – 16 September 2019
The 2019 season for the direct service from London to Avignon starts on 3 May 2019, initially running three times each week, but with four trains per week from 20 June – 1 September 2019 (normally on Fridays, Saturdays, Sundays and Mondays in each direction). But there are of course plenty of alternative routes to the direct train, with multiple options each day requiring an easy change of train in Lille or Paris.
The journey time on the return is a little longer as the train stops at Lille for UK immigration checks.
Avignon TGV station is just south of the city with frequent bus links. And of course with the train you have none of the hassle of airport check-ins and security queues (although there are formalities to go through at St Pancras International)
At other times although there may not be direct trains, you can change at Lille rather than endure the Paris station change.
see more at Rail Europe
Avignon is of course the site of two major UNESCO World Heritage Sites – The Palais des Papes and the Pont St Benazit
By Train TGV from London with Rail Europe