I have combed through everything I could to find out what year that the book 'Good Omens' takes place, it only states what places the book takes us to. So taking this into consideration I thought using the date the book was originally published might be the best point of entry to designing my characters. The book was published May 1st 1990, but I have chosen to look at some British Television police drama examples for inspiration. I am looking to put the characters in a 85-90's environment, I think the following are good examples to designs their costumes into.
British police TV series which revolutionized the genre on UK television in the mid-1970s starring John Thaw as a hard-edged detective in the Flying Squad of London's Metropolitan Police.
Life On Mars
After being involved in a car accident in 2006, DCI Sam Tyler (Simm) wakes up to find himself in 1973, the era of 'Sweeney' type policing, Mark III Cortinas, and flared trousers.
This series chronicled the lives of Bodie and Doyle, top agents for Britain's CI5 (Criminal Intelligence 5), and their controller, George Cowley. The mandate of CI5 was to fight terrorism