[Fashion]
Fashion series 1
John Steed's Fashion
Besides the few photos from the set there also exists some information about Steed fashion in the first episode ever of The Avengers, Hot Snow.

A list of the wardrobe costs names several items of Steed's wardrobe:

Rain coat
Shirt
Grey suit
Tweed suit
Brown sports jacket

source: Stay Tuned Volume 1, Issue 1, p.16