A beerhouse was licensed to sell beer (and possibly also cider, I;m not sure) only. They started in 1830, partially in an attempt to combat the gin palaces. At first any householder who could pay the fee (£2 i think) could set up for himself to sell beer to his neaighbours and could not be challenged by the magistrates. As a result many streets had small converted houses, run by their occupants. Tighter restrictions were soon introduced to control them, but this did not too much affect those already granted, Most by W1 had either been rebuilt into something more resembling our vision of a pub, or had stopped trading, and soem had gained full licenses. At first the majority brewed their own beer, but soon the big (well not so big then) brewers soon started to take over the making of the beer. By the end of WW2 the number of beer-only licenses also dropped to a small number, and i son't think their are any today. In the directories they often list a beerhouse as "beer retailer" and call an off-licence the same thing, which is sometimes difficult
Mike