To work or not to work – that is (not) the question

I am getting to a point where I will make a decision based on the options given to me. What I mean is that if I get an offer from Warwick or the OU, I will request a 4 day working week from my employer. If they refuse, I will resign and try to get project work that allows me to spend sufficient time on studying. I believe that the probability of successfully finishing diminishes with the number of hours worked and 40%-50% of all Phd students will not graduate (Dissertation Genius, 2019). Given my age, I cannot afford to fail and this PhD is more important to me than my job. I am aware this sounds quite privileged but I have worked for so many years in the IT industry which I have come to detest and I want to do something that I feel passioned and might actually create something of value.