Casey76 - congratulations on achieving your lifelong dream for university.
a couple of thoughts :
You clearly have drive and self-control (all that successful studying). So you can decide to apply these to your new goal.
Bearing that in mind, the only way to keep the weight off, however you chose to lose it - is to change your relationship to food.
Look at all the reasons you eat and drink, look at when you eat, what you eat and how much. Really think about the food you put into your mouth, how it makes you feel before and after. Some people find keeping a diary helps.
Once you and food are friends, not enemies and you learn to think of it as something enjoyable in its own right, rather than as a reward, or treat, or punishment, you will find yourself quite naturally eating the right amount for the size you are happiest at (which may not be the slimmest you have ever been).
What really helps is - eating slowly and consciously (so not whilst reading or watching TV or some other activity that takes away your attention from food), always using a plate and sitting down to eat, not banning any foods (you'll only crave them). A 3 week alcohol abstinence can kick start the process because alcohol is empty calories and also reduces willpower. This isn't saying never drink again, just give yourself the best chance to make the changes you want to happen. See how you feel after the 3 weeks. You may like the changes you find.
It has taken you 4 years to put on 3 stones. Respect yourself enough to take the time to lose the weight you want to lose in a healthy, calm and sustainable way. It is possible.