Hobby and SportHomeFighting
Suits, Shirts, Tie Pins and Bowler Hats
Piers Johnson has a fashion section on his website Mrs. Peel...we're needed.
The fashion guide to The Avengers and The New Avengers lists all fashion worn by the main characters in the series.

There's a John Steed's fashion guide for the seasons 3, 4, 5, 6 and The New Avengers so far.
John Steed's Fashion
Fashion in series 1

John Steed's Fashion