When taking the bus in London, if it is cold, sit in bottom in the back row. The seats are right over the engine, and act as bum warmers!
When needing cheap food in London, look for the shops with stalls outside selling fruit and veg in bowls for only 1pound. I've been living off of them for weeks, mostly tomatoes, tangerines and potatoes.
As you getting ready to head to your next destination, make sure you have a good poo right before you leave. You have enough to haul around without taking shit you don't need with you.