A waste of time in one way, Richard, but as you can see it's again stimulated some interesting discussion. Thanks to all for extra info and comments. I'm adding all this to the data to go with the photos - we'll never know the precise dates of these photos but we have some dates we can surmise, at least within a year or two. Locations are sometimes more difficult, but as has been suggested already some intelligent guesswork comes up with likely suggestions.
The next two are a bit more easy to interpret. Clearly this is the front end of a Class 24 with a 501 unit in the background (thanks for confirming the interior shots earlier, Mick) and the lack of a yellow panel will give a bracketable date. I surmise that this was actually soon after the diesel was delivered as there were quite a few allocated to Willesden. Location IMHO is almost certainly Stonebridge Park.
This one gives context to the above. It looks as though the Class 24 is about to be used to remove some Oerlikon stock from Stonebridge Park, and bearing in mind the earlier pictures this is probably on the way to the breakers. That may be a shunters hook on the front of the electric unit.
Brian