[pmyteh]

In the UK you can normally submit without your supervisor's approval if you insist (and have survived the programme long enough to actually have a thesis written). The actual viva will most likely be one internal academic (not your supervisor) and one external and your supervisor won't be present.

That said, it's a pretty crappy idea under nearly all circumstances -- if your supervisor doesn't think the thesis is passable and discourages you from submitting it then it's quite likely the examiners will agree with them. And getting a terminal MPhil isn't exactly a badge of honour...