Display node through panels but limit/deny access directly
By 


  Edit: I'd also like to avoid adding code into template files etc.


do you mean that you want a existing module / UI only solution?  If so, I can't help you with that.

If you don't mind doing a small custom module, this is a somewhat common task that has been answered a few times on this site, and the main SO site, under slightly different titles.

Essentially, you want to redirect a node page to another page or you want to not have a node every viewable on its own.

Two questions worth reading are

Redirect node type to a view

How to prevent access to Views-only content?

Those two solutions can be adapted to your needs.