Well is used instead of really nowdays because people who speak english correctly are considered to be un-cool by chav idiots, it used to be only used by such idiots but now they've ruined the english language for a lot of other people and decent people have started saying it. The correct way to use the world well is at the start of a sentance.
The well is the shelf under the bar where they keep liquor at hand for mixing drinks. So, a well brand or house brand is the brand of liquor served when a customer requests a drink by its generic name (e.g. gin and tonic, scotch and soda). It's usually the least expensive brand served, as opposed to more expensive call brands.