For instance, there is a 1917 clip showing the Lord Mayor of London pinning a DCM (Distinguished Conduct Medal) on one Sergeant North - the caption says 'Brockley, Suffolk', but why would the Lord Mayor of London be in Suffolk. The buildings look like Victorian terracing of the (London) Brockley kind.
Likewise there's a 1931 clip of a folding car - the caption says 'Not sure which county Brockley is in - probably Somerset. May also be Brockley in Suffolk' - but the housing looks very much like round here, maybe even Telegraph Hill? Maybe even Drakefell Road - check out the crest of the hill and the gates next to the house - an entrance to the park?
Have a look and let us know what you think.
On safer ground with the New Cross footage - some great 1958 film of dogs at New Cross stadium, and from the same venue stock car racing at Easter 1954. There's a 1935 film of a Donkey Derby at Milllwall (donkeys on the pitch at the Den, never). The latter was part of an annual Jockeys vs. Boxers charity football match, which is also shown in a 1936 film, where the match was attended by the comedians Gert and Daisy. There's also a 1938 Millwall match against Man. City (check out size of the crowd) and of Millwall v. Birmingham in 1957 .
1935: crowd watching Donkey Derby at Millwall
Update 23 July: walking up Drakefell Road I am now 95% convinced that the folding car footage was filmed there, specifically where the Greenstreet Hill wooden self-build now stands (I believe this replaced war damaged housing). There is still a post box opposite on the corner of Aspinall Road, which you can see in the film. Or am I deluding myself?