Don't do things that poor students in the UK do when playing, don't tip.
London's subway system is quite extensive. Choose the wrong exit, and you might end up walking several kilometers to reach your destination. So, make sure to do your homework before heading out!
British folks have a thing for brand names and love queuing up. Even without supervision, they obediently stand in line. Feel free to try cutting in, but be prepared for some serious side-eye.
"Stand on the right, walk on the left" is the golden rule for London elevators. The left side is the passage for those in a hurry, and standing on the wrong side is more than just awkward.
Smoking anywhere in public or at large events is a big no-no. It's not only uncivilized but could also earn you a fine.
While tipping is accepted in many places in London, there are exceptions. Figure out the situation before giving, to avoid wasting money unnecessarily.
London's traffic rules are strict, so don't think you can jaywalk just because there's no car. Be cautious to avoid getting fined!
Even though London is relatively safe, pickpockets are still around. Especially in tourist spots and crowded areas, be mindful of your personal belongings.