I had a look at the request the website was sending. Then I just pasted the URL “https://www.oscr.org.uk/umbraco/Surface/FormsSurface/CharityRegDownload” into the Unzip Files node and it downloaded and extracted the contents without problem. You can then connect a Table Row to Variable to get the URI of the file as a variable and read in the file with the CSV Reader.
I had trouble reading in that particular CSV file as it contains line breaks in the middle of its strings… Yet to figure out how to deal with that.
Cheers,
Johannes