The OP say that he passed these 2 modules of 20 credits each. Even if they were re-sits/re-submissions, they would still be capped at 50%, and not 0%. I really cannot see a situation where 40 credits out of 180 is treated as 0% as a matter of course, yet that 0% is still counted towards an average based on 180 credits.

I'd like to know which uni this is, and I can go and check on their rules, purely to satisfy my personal curiosity.

Having gone through (and are still in the process of going through) the process of choosing the best uni for a PhD, here is my two-cents worth:

There are no reliable metrics to show the best uni that fit your topic...the best you can do is try and narrow down the field by matching potential supervisors' interest and expertise with your own, and the uni's particular strength in the area of your research interest. How likely you are going to get on with the supervisor is anyone's guess, as a twenty minute skype, or even face-to-face, interview is not going to reveal that much.

In that sense, the best bet might be to stay at the same uni where you did your undergrad/master's, as you would have a much better idea of the personalities of the supervisors. It also helps to talk to the current students of the potential supervisor if at all possible.

Research Ranking can also play a part. At least you have a better idea of the research environment as graded by the REF.

Hope this helps.

Assuming that you are a full time student, you would have done something similar already. Assignment deadlines for each semester usually all fall on the same date near the end of the semester. In a 12 week semester, topics for the essays are usually chosen in week 5-6, so that's 3 essays of 4 000 words, about the length of your dissertation, in about 6-7 weeks.

Even if you are part-time student, the above time scale would suggest that that it's normal to write 12 000 words in about a month and a half. Therefore, you have plenty of time to do a decent 12 500-words dissertation in 2 and a bit months. 4 000 words a week should be very doable if you have an outline planned. Use the rest of the time to edit, polish and proof-read. The best thing you could do is to stop worrying and starting writing. It's not a tight deadline, and you have plenty of time to produce a great dissertation!

Lastly, don't be too concern about grades as you write. Just concentrate on the logical flow, getting your (coherent) arguments across, and proper referencing. It's quite hard to actually fail, and you might well be surprised by your marks if you just get the basics right.