I hope that, in due course, my entire module G12MAN may be made available through the University of Nottingham’s Open Educational Resources pages (and perhaps also YouTube).
For now, here is another sample lecture, concerning the topology of d-dimensional Euclidean space. This includes material on unions and intersections of open sets.
The screencast is available at
I am adding direct links to a selection of my screencasts to the page https://explainingmaths.wordpress.com/screencasts/