Hi TinyPhasma,
I tutor many students who do just this, so it isn't possible but it often boils down to 2 things. What type of student you are and how demanding your course is. Some courses demand more time outside of lectures than others.
Some OU students, for example, hold full time jobs whilst studying. I don't want to go into too much detail here, but if you find my website you can see my professional background before I moved into tutoring. I did all my studying whilst working. I am currently tutoring someone through their MA who is head of loss protection for a High Street brand and he works full time. Most of the undergrads I work with have jobs and I think this enhances their CV and gives them a more grounded perspective. There were some horror stories too, another of my students had to work 30 hours per week just to survive. The pressure got too much for her and she ended up leaving, but will be coming back in September.
I think if you are very well organised with your time and be strict and realistic with yourself, you could have a good guess as to whether it will work for you.
Good luck.