Find a good deal on your flight from London to Lourdes/Tarbes with Netflights. If you want to keep your options open, take a look at flights from another airport in London.
But when you fly is just as important as who you fly with. If you're flexible on dates, try searching by month to see when the cheapest flights are.
If you want a bargain Or you could broaden your search by looking at flights to other airports in France to see if there are any cheaper options.
Did you know you can also compare car hire and hotel prices in France with Netflights? Take a look to get an idea of prices in Lourdes/Tarbes.