I've come to realise that most things are possible with SilverStripe, it's just finding out how...
I'm sure I must be able to constrain in some way the types of pages administrators are able to create in the CMS. For example, following on from the second tutorial, we have a News page which is of type ArticleHolder, which contains a number of ArticlePages. As it stands, though, there is nothing stopping me creating any other type of page as a subpage of the News page. Is there any way that firstly I can ensure that the News page type cannot be changed from ArticleHolder, and secondly that only pages of type ArticlePage can be created as children of the News page?