Our train was at 6.30 am, and we were there about 5.45, and there was stuff open then. Plenty of people about too. BUT we were there on a Monday morning, and although they told us to wait in the terminal, it turned out there was reduced capacity on the train because of engineering works at the weekend and although we joined the queue when we were called we did not get on that train. Even more annoying, they didn't tell anyone, so cars were left just sitting there and eventually people got out and asked what was happening and the story filtered back. Officially however we weren't told anything just left to sit there until the next train at 7.30.
So the moral of this rather long story is that I'd be wary of hanging round long in the terminal especially if travelling on a Monday.