Cobham is recruiting constantly, do not worry. It will be ground school after ground school for monthhhhhhsssss. But they are taking internal transfers first before they call up someone off the street who has just applied. This would be why internal transfers or people with previous aviation experience are getting called for interview the day after they apply and everyone else is waiting a few weeks. They have lots of people to get through and see but there have also been some no shows. Don't lose hope. They will be doing a lot of AD's too. It's just at the moment they are in a hurry so people are going straight to interview rather than going through the whole rigmarole of an AD.
If 4 crew comes back for the 717s, and I'm told it will by July, they need at least 70 new crew. That is a lot.
Like has been said - arrive early, be eager, be polite, shake hands, be genuinely interested, present your paperwork formally, not just in some ****ty plastic sleeve, dress well, come prepared with lots of stories about your previous aviation/hospitality experience to tell, don't walk in thinking you've already got the job (or walk in with a typed list of 35 questions about the contract on offer like one candidate did) and do emphasise the importance of being a team player.