They can't confiscate your personal property, that would be theft... a criminal offence.
In fact they aren't even touch you physically if you haven't gained entry by force...all said, the secs there even though they always catch people [usually after being inside for the shot] aren't your typical big secca blokes....if you humour them they can be quite pleasant and I imagine are quite delighted us lot go there to give them something to do...must be a bit mind numbing just sitting in a car all day....