As you say, the precription charge is reviewed annually and the cost is recalculated, always upward to allow for inflation and to cover costs (or a% of cost). It will begin during the next financil year.
The rest of the budget is not annual, but is the whim of the present Chancellor. It is a money raising exercise, so one year he might hit drinkers, and the next year he might leave them alone. The mix is variable, and therefore cannot be annouced until the Chancellor lays all his plans out.