Duty rises and a ban on below cost selling would seem to me to be a better way of controlling price than Min unit prices, at least that way money flows to the government coffers. Supermarkets use booze to drive footfall, petrol, flat screen TVs and booze are the 3 lowest margin products on sale in your average superstore.
Finally those of you doing the maths to say 45p/50p per unit is perfectly acceptable wake up! this is the thin end of the wedge, once the principle is established watch how it accelerates.