If you're looking for a beautiful large sandy beach in the South of France, look no further. The Narbonne Beach is a lovely long sand beach located around 15 mins drive from Narbonne. The best time to go is in the Summer months to guarantee warm sunshine and plenty of time for sunbathing. Otherwise a weekend in Spring would be nice too and less busy. It depends what kind of weather you're after, and if you want tourists there too or not..
I wouldn't recommend going on a cold grey day like I did, but a nice hot day in Summer would be perfect. There are several restaurants selling pizzas and pastas and such like. There are lots of shops selling inflatables, ice creams, sun cream etc.
You could easily go there for the day and not need to go anywhere else. The beach had lovely fine sand which is normal in that part of France, but for me coming from near Marseille it was a bit of a luxury. Beaches close to me are rocks and pebbles and it's hard to find a nice natural sand beach.
There was plenty of free parking too, although in Summer I imagine it would be harder to find a place to park.
When I was there, there was a Spanish festival on. There were lots of dancers, singers and Spanish food tents. I think they probably have other events on like this over the Spring and Summer months, so keep an eye out on that.
If you're in the area, I would also suggest visiting Narbonne city centre for some beautiful architecture, lots of history and generally a lovely city to walk around and explore.
If you're looking for somewhere to stay, I can highly recommend these places below. Both places are a couple of minutes walk from the beach and shops, have an outdoor swimming pool and free parking.