While many modern shows like Breaking Bad and Game of Thrones may be multi-award winning cinematic television, British television is just as respected without anywhere near as much scale and scope. Shows like Doctor Who and The Office demonstrate that many of our shows can be enjoyed across the globe, while comedies such as the IT Crowd and The Inbetweeners are critically acclaimed for their comedy, usually more realistic and less over the top than similar American television.
British comedy is such a part of the nation's culture that the public therefore share a generally universal understanding of many sayings, quotes and characters from it. It's so prevalent that people may know a range of quotes from a show without having ever watched it themselves, or they'll maybe be able to quote a series to you word for word without fail. Therefore there is almost a small extension to the British language that is almost entirely made up of quotes and sayings from famous TV shows.
Some shows, however, are timeless, and they continue to be quoted to this day - years after leaving the air.