It is also true, as jaimeelsabio above says, that sometimes it's quicker to get off the bus and walk when it's really busy. The technique if you're in traffic between stops is to go to the front and ask the driver to open the front doors for you. It's probably sort of against health and safety but some drivers will do it. Be careful if you're then stepping out into traffic.
Sometimes a bus will terminate early to "regulate the service" when the roads are really congested. If there's three buses tagging along beside each other on the same route, chances are that one of them may terminate early. Just get off and then get on the next bus of the same route number that comes behind. Not tapping in if you've just transferred from a terminated bus is fine.
Queuing at bus stops that serve multiple routes is quite informal. Not everyone is waiting for the same bus as you. My general rule is to hang back for women with children, the particularly elderly, anyone with mobility issues, etc. and let them go first if possible. If more than one bus on the same route arrives at the stop at the same time, it's often advantageous to walk to the bus behind. It's often quieter if it's been tagging along behind another busier bus.
The OP may know all these things in this thread about buses if they've lived in London for a year. Apologies if so!
