A box of choccies may work, who knows?! As for individual circumstances, I can't say why one individual is selected for interview and not another. All I would say is look very critically at your CV - and get someone else to do it too. If it's not crystal clear, limited to a single page, and has your experience and contact details clearly decipherable, you won't stand a chance!
This only applies to those who applied using a CV and are keeping it up to date (only once a year please, unless there are very significant changes!). All new applicants must apply online.
Scroggs