According to the British Soft Drinks Association some 45% of carbonated drinks are "regular" rather than "mid" or "no/low" calorie at 6 and 49% respectively. With a 2014 volume of 6380 million litres of total carbonates that makes 2870 m litres of regular sugar sweetened beverage so the proposed levy looks to cost 18 p/litre (25 US cents).
With the detail to be worked out and various exemptions for small producers etc the exact cost implication to the consumer remains to be seen. The sugar in a litre of 10% SSB probably costs ~4p so this levy is substantial compared to the manufacturer's costs.
There are two bands of levy proposed :-
Soft drinks industry levy