Having been in the situation often enough, i can also tell you: I wouldn't mind if cars passed by me in narrow situations if they slowed down while doing so, but more often than not, cars pass by at full speed instead.
Lastly, keep in mind that this situation only happens in narrow side streets, not on big streets with better separated traffic flows.
Sport cyclists taking a whole lane while ignoring a dedicated bike path are just assholes.
There are of course provisions to dissuade or prevent vehicular use which is purposefully obstructing, but my purpose is not to obstruct. Its purpose is to aid in the enforcement of rules which state vehicles must pass cyclists within certain safety limits, which they do not adhere to of their own.
I have a moral right to not be killed by impatient people. I do not just "feel" unsafe in my designated lane: I am unsafe. Cycle paths, in the UK, are not mandatory for any users, precisely because they are not always suitable. Until the UK's highways are no longer for the public there will never be a time where I am not entitled to safe passage on it.