I'm in Provence.
We used to live in an overseas département with a huge diversity of populations. We were stunned when we arrived here. Forget Peter Mayle: we live in a once prosperous, run-down, dirty town centre with a high Northern African and gitan population, unemployment, petty crime, drug dealing and a growing accommodation problem. The tension is quite palpable and frequently spills over into knife fights, or 30 guys with baseball bats and sundry other weapons out to "get" a gitan following an exchange of pleasantries. Anyone who can afford it lives on a lotissement on the outskirts.
When we were looking for a place to rent, people openly asked us over the phone what we looked like before agreeing to show us properties. One black woman explained later that she suffered so much racism from "les Arabes" that she would have been scared to show DH round the flat if he had been North African.
I think anti-Algerian feeling is stronger in the South because many of the pieds noirs settled around the Mediterranean on their return to France and have remained very bitter. Older immigrants from Italy or Spain are also very pro-FN, paradoxically.
What strikes me is the openness of the racism; people assume that their views are shared by all, and feel free to express them vocally.
You do definitely need to come over and get a feel for different towns; ours is extreme, and is the only one like it in the area. Perpignan was hit by raging battles between gitans and North Africans not so long ago, while neighbouring towns are calm.