Multiple nodes within a node Does anyone know if there's a module out that would provide the functionality for displaying multiple nodes within a node i.e. similar to how a blog looks with its articles, simply a page that displays a number of teasers that link directly to other nodes.

The big thing would be the CMS part and the ability to add existing nodes within a node. By this I mean like the way you would with a field, except in this case it would be a list of existing nodes.

So far my attempt at such as set-up has been to use the field collections module to put a few fields together like title, image, long text, etc, then use this field collection as part of a basic page. This does exactly what I'm after except all we are doing here is giving the content manager the ability to supply a path to an existing node so there is not relationship here at all. 

A content manager could delete the node and forget to delete the teaser on another page that was linking to it.

Please could I stress that 'Node embed' is not an option or anything similar because its just not practical for clients to use such methods. It needs to be very simple that almost requires them not to think.

Any suggestions please?
Sounds like you need to use entity reference module and have it render the teaser view mode. 

This field can have unlimited values so you can keep "adding more". This will allow you to specify nodes to embed in another node.

Alternately you can use field collection if you do not require these embedded nodes to be a node on their own. 

Furthermore you could even add a view which shows teasers as a block to bottom of the node, however the filters / contextual filters will be more dynamic in nature rather than manually selecting specific nodes. You could argue that node queue would allow you to do this but I would say thats a lengthy way of resolving you question.