I'm not sure where you think 'bullying' comes into this? Nothing you've said here constitutes bullying.
So, because they wont let you do more hours or take time off work for a college course (the two requests seem a bit contradictory to me) and have stopped you using the internet during office hours, you feel stressed and have gone off sick? Personally, I'd say that you're lucky to still be on the payroll after being off 'sick' for several months.
In any case, the first step would be to raise a grievance with your employer. An employment tribunal comes later, if necessary. I can't see either succeeding given what you've said here.