Upload your passport scan on the Study Abroad page.
See emails from Study Abroad office about medical clearance and other small to-do items.
Buy a UK adapter for all your electronics and other items that you'll want to plug in.
Check with your cell phone provider about adding an international plan and what your costs will be if you make calls. Plus let them know the dates you'll be abroad.
Add the free Viber app to your phone.
Find a London Underground (Tube) and perhaps a walking map app of London to add to your phone.
Call your bank and credit card company to see what foreign transaction fees or other charges they might have. Plus let them know the dates you'll be abroad.