Read an interesting article on anna.aero recently regarding Flybe and it's position at UK Airports based on this month.
It appears that Birmingham is still the top base when looking at monthly seat capacity changes, but is only ahead of Manchester by just over 500 seats (Birmingham seat capacity is down by 2.1% with Manchester growing by 9.1%) Overall seats for Birmingham for the month were listed at just under 116,000 (I assume this is based on both arriving and departing seats ?)