First, feel sickeningly overwhelmed as you stand on the brink of such an endeavor. Spend a couple months wondering what on earth you could have to say that would fill so many pages. That accomplished, Have. A. Plan. and feel the panic subside. Take it in baby steps.
Then, fall behind on that plan. Start hiding the plan from yourself as it becomes more and more unrealistic. Finally, convince your supervisors that it is perfectly alright to scrap half of what you planned. When they agree, feel the panic subside. Again. Carry on with baby steps.
Work really hard some days, from 8am to 8pm. But usually, completely ignore your work for days at a time, waiting for your subconscious to pull it together. During this time, marvel at how many lovely diversions Europe has to offer. Plan trips, take trips, paint stuff, make friends with the wildlife on evening jogs. Ride your bike along country lanes. Bake a lot. Clean your flat with uncharacteristic thoroughness. Convince yourself that all these things are much more important than finishing a silly degree. ...In fact, except for the cleaning, they most certainly are.
When you finally submit a draft of Chapter 3 to your supervisors, ignore the fact that you had planned to finish it last December. Apologize that it is 100 pages long and breathe a huge sigh of relief that now it's weighing heavily on their shoulders. Buy yourself a ticket to China.
Next, laugh with never-ending surprise at how you're now halfway to a PhD (you're gonna give me a degree for this? alright...) Marvel at how close you were to not doing this: how close you were to not daring to move to England with all its unknowns, and how close you were to not getting a scholarship.
Thank your lucky stars, every single day. And then carry on with baby steps.