so to go straight in at daily seemed a little high
You're not seen as serious at less than daily as it's the people down the front they're chasing and they demand a flight when they want to fly, not when the airlines prefers. They're going up against Swiss so a major player with home advantage and frequent flyer loyalty, no half measures methinks.
At MAN, there's no home carrier on the route and they have an existing connection loyalty with BA over LHR they can tap. Less risk, but ZRH does I imagine, have the higher reward. Or possibly not?