Unluky robber Lenny Cudlip (Darryl Clark) uses a snub nose revolver during the robbery of Dame Bianca Norman's pullman wagon in "The Great Train Robbery" (S07E01). The gun looks S&W style, with thumb cylinder release, unsupported ejector rod, large grip with lanyard ring, but lacks front sight. A possible guess is a standard Smith & Wesson revolver, like Military & Police Model that has the part of the barrel with ejector rod socket sawed-off. A revolver with same outlook, most likely same prop, is seen in Season 5.
Webley .38 Mk IV Duty Model
Lenny Cudlip's brother Daryl (Andrew Turner) uses a Webley .38 Mk IV Duty Model during the robbery in "The Great Train Robbery" (S07E01). A Webley .38 Mk IV Duty is seen next to dead Lionel (uncredited) in "The Blood of the Anarchists" (S07E08). In flashback scene this revolver is in hands of Angus Boyde (Kevin Mains).
In "The Honourable Thief" (S07E10) Hercule Flambeau (John Light) holds a Single Action Army Artillery model revolver (a very strange choice for gentleman thief of 1950s). The revolver is completly black and seems to be kind of a non-firing replica. Very likely it's the same prop that was used in Season 1.
Pistols
Walther PPK
A Walther PPK is the murder weapon in "The Great Train Robbery" (S07E01).
Browning Hi-Power / Kareen Mk II
In "The Sacrifice of Tantalus" (S07E06) Special Branch Inspector Sullivan (Tom Chambers), acting under the name of Inspector Trueman, carries a Browning Hi-Power. He then hands his pistol to Chief Superintendent Len Blaisen (Sean Gallagher). This gun has "Type 73"-style hammer spur and non-standard wide slide serration, like Hi-Power pistols, seen in Seasons 3 and 4; this is supposed to be a Kareen Mk II slide on a standard Browning Hi-Power frame.
Rifles
Lee-Enfield No.1 Mk.III*
During the police operation to arrest Cudlip brothers in "The Great Train Robbery" (S07E01) Inspector Mallory (Jack Deam) and Sergeant Goodfellow (John Burton) are armed with Lee-Enfield No.1 Mk.III* rifles. Jimbo Riley (James Cartwright) holds a No.1 Mk.III* rifle in "The Demise of the Debutante" (S07E04).
Lee-Enfield No.4 Mk.I
Four constables are armed with Lee-Enfield No.4 Mk.I rifles in said scene in "The Great Train Robbery" (S07E01). Some of these rifles have angular magazines, indicating that they are chambered in 7.62x51mm NATO (like unsuccessful L8 series).