I will be in Provence in early September and staying in Saint Remi - is there any chance that I will catch any sunflower fields in bloom or can anyone recommend another bloom to search for?
It depends on the weather conditions and the region but generally sunflowers are harvested between mid August and mid September. And at harvest time they are not as bright yellow as they are now, they have turned brown.
(I am further west than Provence but I am surrounded by sunflower fields)
Early September you should see some.