From the Evening Standard:
The system of measuring alcoholic drinks in units could be scrapped under plans unveiled by the Conservatives today.
They say units are widely misunderstood and fail to take account adequately of differing strengths of drinks, such as beers and wines.
Unveiling a raft of public health reforms, shadow health secretary Andrew Lansley said units would be replaced by the actual number of centilitres of pure alcohol contained in each drink.
From Wikipedia:
In the United Kingdom, a unit of alcohol is defined as 10 millilitres (or approximately 8 grams) of ethanol (ethyl alcohol).
Problem solved!