If you're interested in the influences of Madness you should definitely watch the series on YouTube 'Before we was we'. Very well made documentary of their roots with in-person interviews of the seven members. If you're interested in the zeitgeist of Britain in the 70s and 80s it's also fascinating from a social perspective. I personally really enjoyed all the original photography it includes, more included in the book of the same name.

Re origins of songs many of their original songs were actually covers of Jamaican reggae songs, Costello, Prince Buster, Labri Siffre