May be the Goldfish bowl operator can give us the true picture regarding slots at FACT. I find it hard to believe there can be a "lack of slots". I'm sure many UK provincial airports handle more movments than FACT does. But departure gates - that's a different story. From memory it seemed that BA for instance arrive early in the morning but then sit on the tarmac all day - this keeping the stands (and there's not that many) from being used by other aircraft.
Not sure how accurate a picture I'm painting but surely if the long haul carriers could turn around quicker - may be FACT could accommodate more long haul stuff? Then again I guess the likes of BA have probably taken account of many different factors in determining their schedules.