This will not help answer your question but makes interesting reading all the same:
Brief history of beer duty - From the HMRC website.
Excise duty on beer is the oldest source of revenue still collected by the government. Attempts were made to tax beer by both James I (James VI of Scotland) and Charles I. It was in 1643 that a proper excise duty was first imposed on beer, initially as a measure to raise cash for the Parliamentary forces during the Civil War. When the war ended, the duty became a permanent source of revenue and the Excise Service was formed. Two classes of beer were recognised - strong and small - and duty charged at corresponding rates on the quantities brewed. There were many thousands of Private Brewers (home brewers) who presented considerable problems for the collection of the duty and in 1653, home brewing became exempt.
At different times duties were placed on malt and hops and so the tax paid by the Brewers For Sale included the beer duty and the duties on the malt and hops, whereas the Private Brewer paid only the malt and hops duties. The difference in duty between strong and small (weak) beer caused considerable adulteration and fraudulent mixing and consequently the revenue regulations were numerous and restrictive.
In 1830 the Beer Duty was withdrawn and only the duties on malt and hops remained. Revenue from hop duty fluctuated greatly because of the uncertainty of the crop and so in 1862 it was removed in exchange for an increase in the Brewerâs Licence duty. As the duty was now only on the malt, brewers were prohibited from using malt substitutes, until in 1847 they were allowed to use duty paid sugar.
The duties on malt and sugar were duties on raw materials. As a result, the accumulation of the profit on the duty outlay of the malster, brewer, and dealer; the inflated price of the best brewing barley; the use and loss of duty paid material during production and the restriction on the use of materials, made the price of beer expensively disproportionate to the amount of revenue collected. Mr Bass (an MP) stated that in order to collect £8m of revenue, £25m worth of beer had to be sold.
Consequently, by the Inland Revenue Act of 1880, the duties on malt and sugar were replaced by the Beer Duty. This was now based on the gravity of the worts prior to fermentation - that is, the Original Gravity (OG) of the worts. The introduction of the saccharometer and original gravity tables in 1874 had contributed towards the decision to change, as there was now an accurate way of establishing the strength of the beer. At the changeover the rate was set to equate to the duty previously charged on malt. This was achieved by deeming that a given quantity of malt would produce a standard volume of beer at an OG of 1055. There was much argument from the trade as to the accuracy of the basis of this conversion. Times do not change.
On 1 June 1993 the worts based system was replaced by the current arrangements under which the duty is charged according to the alcohol by volume (abv) of the finished product. Thus, for the first time in the UK, the beer duty charged is directly related to the alcoholic strength of the beer. The introduction of the current system brought the excise treatment of beer into line with the other alcoholic drinks regimes in the UK as well as implementing the EU Directive on the harmonisation of excise structures necessary for the completion of the Single Market.