From 1st May a new direct rail service starts leaving London St Pancras at 7.19am arriving in Avignon TGV station at 14.00 where you can rent a car and drive the short distance to the Luberon. By 16.00 you’ll be on the terrace with a glass of rosé! The return trip leaves at 16.00 and you will be in London just after 22.00.
Trains stop at Ashford international, and then Lyon, Avignon and finally Marseille. In May, June, September and October there are three services a week (Monday, Friday & Saturday) whilst in July & August there are five services a a week (Monday, Thursday, Friday, Saturday & Sunday) . Remember this is just the direct route, you can easily travel via either Paris or Lille anytime. For further details http://www.eurostar.com/uk-en/south-france-holidays