Aha I knew that my status as a French gardener would come in handy!!
The Dordogne has a very mild climate and I think you can probably start a little bit earlier than in the UK. The person should be able to grow very delicious tomatoes, sweetcorn, melons and squash!
The others are right, there are many veges that the French tend not to grow such as parsnips (they grow very well here! Just get the seeds from a catalogue like I did) but there are other delicious things they do grow, like many dried beans (the famous "Mogette de Vendee"), celery root, and different types of salad veg, such as lamb's lettuce. Also what we call "cow cabbage" here which is a winter cabbage that forms only green shoots, no actual cabbage head (dunno what that is called!). But we probably get more sun here on the whole than the UK so the tender veg probably grow better.
From what I have seen so far of French gardening, they are quite fond of chemicals, weedkiller, fertilizer etc and don't seem to go in for mulching (hench the strange looks I get). They seem to eye organic gardening suspiciously, although it is in vogue with younger gardeners.
I ordered a lot of things from a web site called Willemse, which delivers in France, and they have a good selection of veg, lots of variety and the prices were cheaper than in the big French gardening centres. In rural France, you can buy veg plants from market stalls often, the flower sellers usually have trays of baby plants at this time of year.
Hope this helps a bit.