Recently I posed a question on the Masters Forum regarding M.Phil. based on published works in the humanities and asking which universities might be able to assist. Alas, despite a large number of readers no answers were posted.
Now I will try a different approach. Can anyone suggest a university possibly willing to register me for a Ph.D. based on published works but which might be prepared to fail me and to offer a M.Phil. instead?

Stirling offer a PhD by publication...

You can do a PhD by publications though they're not generally done very often but if you have enough papers you could have a chat with whatever perspective uni you want a degree from and see what they have to say. It can be done. But if your intention is to do a M.Phil by publication why don't you pose this to the uni in question? It would require less papers so I imagine they might be ok with it.

Anglia Ruskin University at Cambridge do both a Professional Masters and a Professional PhD based on published works.

Out of curiosity, what are the chances of passing by doing such a degree? Does everything depend on the standard of the journal (eg. ISI)?

Just curious to know! Why would you want a failed PhD with a view to obtaining an MPhil? I'm unsure of MPhil by publication. However, a small number of UK universities (e.g. The University of Birmingham, Queen's University, Belfast, Sterling University, etc) offer PhD by Publication. Some of these unis (e.g. Birmingham) only allow their academic (i.e. teaching and research) staff into this route. Use google search engine and I'm sure you'll get more than enough info on this subject. Hope this helps.