Difficulty being admitted to good PhD programs in the UK Since last September I have been working hard on my applications, applied to multiple good CS departments yet none of them even wait-listed me, all rejected me, I have also got rejected informally by supervisors I approached.

Now I know I am not an established researcher in this field, I did not publish anything yet nor I have a concise experience with a certain topic but I know that I am not far off and I can pull my weight to reach the desired level by a number of the departments I applied to. The issue is that I almost all the time get unfriendly, cold treatment from professors, none of them is willing to take 5 minutes to discuss anything.

I am told that professors will always accept me even if I had average or below average marks because I am bringing my own fund for this degree yet this whole notion seems false.

My master's transcript does not look good, I have failed 2 courses and recovered but that 'F' will always look like a stain on my transcript. My bachelor's transcript is average (upper-second in UK scale).

How can I improve my chances to get into a PhD field that is not far off what I did in my master's?
You seem to be operating on the assumption that "I have my own funding, therefore, I can go wherever I want". That is simply not true. Taking on a graduate student is not only a matter of money, it is also a significant investment of time on the part of the advisor and believe me, at top departments, time is a more scarce and precious resource than money. If the professor does not see a reasonably good chance that this investment is going to result in a comparably good outcome (i.e., a student with high-profile publications and a strong thesis), then very likely they won't take you, even if you bring your own funding.