Recently my friend has had his saxos wheel arches stolen, alot of other cars near my college have also had parts being taken off them.
It appears there's a thief operating in the Southampton/Eastleigh area who takes a photo of your car part posts it on ebay and if he gets enough bids for it steals it the night the auction ends. He's being reported soon however he/them will most likely still operate for a period until they are banned.
You should be fine if most of your car is properly welded on like newer cars but for those of you with more of a kit car style or easy to remove spoilers/body kit you might want to think about putting your car in the garage for a little while.