Alex, thank you for this!
I can get this to work as in your example when people click on “Read More” requesting a premium article and get redirected to the Subscription page whereby they are told that the article they want access to is a Level X article. From what I can tell, your code needs the user to request the article (by clicking Read More…) before this message can be returned.
However I would also like to show what level each article is in the main loop on index.php without the article actually being requested.
Here is an extract of a screenshot of my main loop. The first two articles I have allocated as Level 3. And when a Level 1 user clicks on Read More, they are taken to the subscription page and your wonderful code does its work. But as you see in the right hand column where the meta data is, the same code always returns the last line, “Already a member?…”.

Is there a way to tweak your code in order to show it on the main loop here?
Thanks a lot