To look at things from the opposite view of the earlier list (Tory seats held in opposition but not now), I see that, of the 52 constituencies held by Labour in their big 1931 defeat, 17 are not held by them now:
Broxtowe (now Conservative)
Clay Cross (Conservative)
Don Valley (Conservative)
Dumbarton Burghs (Scottish Nationalist)
Glasgow Bridgeton (Scottish Nationalist)
Glasgow Gorbals (Scottish Nationalist)
Glasgow Govan (Scottish Nationalist)
Glasgow St. Rollox (Scottish Nationalist)
Glasgow Shettleston (Scottish Nationalist)
Hamilton (Scottish Nationalist)
Leigh (Conservative)
Mansfield (Conservative)
Newcastle-under-Lyme (Conservative)
Rother Valley (Conservative)
Rothwell (Conservative)
Spennymoor (Conservative)
Workington (Conservative)
Of these, seven are in Scotland (and now held by the SNP), six in the North of England (now Conservative), and four in the Midlands (also Conservative). Most, but not all, were lost in the last three elections (the Scottish ones in 2015, the rest mostly in 2019).
[Should probably note that the old Broxtowe constituency is mostly modern-day Ashfield & Sherwood, while the new Broxtowe is largely cut from Rushcliffe.]
Of those, places who were Labour non-stop from 1931 to 2019.
Clay Cross: All parts who are in current day Bolsover i.e.:
Former rural district of Blackwell (all of current Bolsover district south of Bolsover itself)
Current North East Derbyshire district wards of Holmewood and Heath, Pilsley and Morton, Shirland, and Sutton
Don Valley: All of current Don Valley
Leigh : All of current Leigh (excludes Atherton, which is now in Bolton West)
Newcastle-under-Lyme : All of current Newcastle-under-Lyme (excludes Talke, which is now in Stoke North and was in Leek in 1970)
Rother Valley : All of current Rother Valley
Rothwell : Parts in current Wakefield constituency (Horbury, Crigglestone, West Bretton, Sitlington, Lupset)
Spennymoor : Parts in current North West Durham (Tow Law, Stanley, Hedleyhope, Crook, Howden, Hunwick, Helmington Row and Willington) and Bishop Durham (Spennymoor)
Places which are on the list but voted non-stop Labour since 1931 (including 2019)
Don Valley: parts that are now in Doncaster Central and Doncaster North
Doncaster North: all the constituency but Adwick and Bentley
Doncaster Central: Armthorpe, Edenthorpe, Barnby Dun, Kirk Sandall (in other words, all but Doncaster town)
Rother Valley : All of 1931 Rother Valley not in current Rother Valley
Sheffield South East : Handsworth
Wentworth and Dearne : Swinton, Hooton Roberts, Thrybergh, Ravenfield, Bramley, Wickersley
Rotherham : Dalton, Brinsworth, Catcliffe
Rothwell : parts that are now in various constituencies
Leeds Central : Middleton
Leeds East : Temple Newsam
Normanton, Pontefract and Castleford : Warmfield-cum-Heath
Hemsworth : Sharlston, Crofton, Walton and Chevet
Spennymoor : parts that are in current City of Durham (Brandon and Byshottles, and Brancepeth)
