From the Australian Governments Travel Advice website dated 15 June 2017, under Crime :

"Thieves commonly target motorists, especially (though not only) along the Mediterranean coast from Marseille in France to Valencia in Spain. They might try to convince you to pull over because of an apparent problem with your vehicle, or offer assistance to change a slashed or flat tyre. While one assists you, an accomplice steals from the car. Cars with foreign number plates are often targeted. Thieves have also broken into caravans and motor homes, particularly in public parking areas."

I would like to know how prevalent this really is. Is the Australian government being overly cautious? Have things worsened with the increased numbers of immigrants?

Our lease car will have French lease car number plates which appear quite different to standard French number plates and do stand out a bit. It is for this reason that we are a bit concerned.

At night we remove everything from the car and leave the glovebox open. During the day luggage etc would be covered.

Any thoughts?