I also am in seq and have the exact same prob. In the last mth or so my bees have nastied up.
the prob hive is the same as yours 1 brood 1 super 1ideal super on your top. After I disturd the hive it takes them several days to calm down, during that time single bees will buzz me and family up to 20m away.
when you split your hive did you requeen or let them make their own queen.
Does anyone have personal experience with requeening with so called quieter strains of bees, was it effective.
I re-queened them myself with a queen from a local'ish queen supplier. I am very very keen to try some of John Covey's caucasians (the grey ones, right?), as I've heard that the race can be very quiet (unfortunately there were none available when I needed one).