AC 428 Convertible in Invasion of the Earthmen - Licence Plate: LPH 800 D
The Rotters - Steed driving Tara's red Lotus Europa PPW 999F. Steed deliberately attempted to wreck Tara's Lotus in Stay Tuned when he heard the word "Bacchus", but Tara was driving in that episode.
Steed is leaving the conference in Two's a Crowd in a Humber Imperial from 1964 with the licence plate: AWK 948 B or AWX 948 B.
It has to be an office car, as members of the delegation arrived in then same car at the beginning of the conference.

Photo 1
Photo 2
Audi 100 in TNA Angels of Death - strange licence plate, definitely not a German one as after the  "M", which would be Munich, have to be letters and not numbers.
Mercedes Benz (1960/59?) 190 W110 or W111 in Dead Men Are Dangerous.
Licence Plate: B-NP-374; B= Berlin
TNA K is for Kill - The Tiger Awakes

1977 Rover SD 3500 left-hand drive
French licence plate ends with the number "95" which indicates Val-d'Oise, region of Ile-de-France
Licence Plate: 4253 BW 95
Steed's driving an Army Jeep in TNA episode K is for Kill - The Tiger Awakes.
Licence Plate: 785 CA (I 4)
John Steed sitting in 1960 Morris Mini MK 1 in How to Murder. He's not driving the car, but follows Henry by taking the bus.

Steed also drove:

1977 Green Toyota Land cruiser J40 in TNA Forward Base.
[The Bentleys][Home][Macnee's Car]
1956 Olive Green Land Rover 88'' Series I (VX 897) in A Sense of History and Never, Never Say Die
1961 Land-Rover 88'' Series II (OPC 104D) in The Hidden Tiger
The Avengers and all images from The Avengers are
Copyright © CANAL+IMAGE UK Ltd and respective licence holders.
No attempt to infringe this copyright is intended.

Steed drove a second car, a 1965 Triumph 2000 Automatic Mk1 (MBH 545 C) in Requiem.
The first car that Steed used in Requiem is a 1966 Austin A60 Cambridge.(LGF 9420)
Information about cars used in The Avengers can be found on the IMCDB site.
Steed drove:a 1967 Triumph 2000 MK 1 Automatik (DHM 243 D) in They Keep Killing Steed.
Steed is driving an amphicar in Castle De'Ath.
Other Cars