Season 1 Episode 3: Rachel in Danger (part 3)
A man flags down a London Transport bus. It's RT935 (JXN325), which by the time this was filmed was in preservation.
Season 2 Episode 7: Dead Man's Kit (part 1)
Set partly on a Royal Navy ship. As the seamen disembark at Portsmouth Dockyard, seen in the background is a Portsmouth Transport Leyland-National and no less than three Leyland Atlanteans, although none is clearly seen:
Season 2 Episode 23: The Circe Complex (part 1)
A man in a Morris Traveller is tailing a man who catches a bus. It's CK Coaches of Cardiff 25, but we only see distant or extreme close up views of it. I'd welcome a definite ID, but I believe it's a Daimler Fleetline/Park Royal new to West Midland PTE.