"Your aircraft, likely an Airbus, has about 20 Business class seats (5 abreast)."
All depends on the booked load, as to how many seats will be allocated to Business class. Bmi have a moveable cabin devider so can increase/decrease the amount of seats depending on the booked loads in each cabin for each particular flight. (the curtain row is set by the Dm on shift the previous night.)
Minimum will be 1st, 3 rows, but is usually more depending on flight time. The teatime flights will almost all be Business seats, whilst a mid afternoon flight will be mainly econ seats.
The only differance in service o/b is what you get to eat. In business you get a 3 course meal (snack) served on proper plates and a seat thats about 2 inches wider, whilst in econ you get a pre packed sandwich, and a slightly smaller seat. In both classes, the rest of the service (and leg room) is the same.
"She Rolls, 45 knots, 90, 135, nose comes up to 20 degrees, she's airborne - She flies, Concorde Flies"