The minimum age for drinking alcohol is 18 years. For such a small place there are a lot of bars and quite a few different clubs. Despite duty on alcohol being lower than the U.K. most popular bars set their prices close to what you'd expect in London. Normal pub closing time is 11PM and most clubs have to be closed by 2AM there is no "drinking-up-time". There are a few bars with alfresco areas including one with a view over the bay toward Elizabeth castle. Most of the working-men's pubs became trendy wine bars in the early nineties so there's not much chance of finding a pool table in town. There are two bars which sell Absinthe.
There is quite a good music scene, in part due to licensing regulations which allow some bars to stay open till 1AM if they have live entertainment. The bars with a late licence never have a cover charge but all the clubs do.
The main town of St. Helier is compact enough that you can wander from pub to pub and club to club quite easily.