10 a day or 20 a day?
If you can only buy them in 20s, seems to me it's more likely people will smoke thro' the whole 20 in a day, whereas if they'd only bought 10, they might just manage to spin them out till next morning: so this idea is a double-edged sword! (BMA take note of one of your own members' opinions, since you have also promoted this idea of 20s only discouraging youngsters!)
TB