Update: it appears that the above issues were caused by having set a content character limit in Appearance > Customize > Content Archives. I’ve changed it back to 0 now which has resolved the issues, however I do need to find a way to change that setting without it affecting the Events page, is this possible? Thanks.
Nico, this is all excellent, thanks for your help!
One query: the past events page has the most recent past events at the bottom of the page instead of the top, is there a way to change the order so that they appear in a more more logical order?