The London Underground (otherwise known as the Underground or the Tube) is a metro system serving a large part of Greater London and parts of Buckinghamshire, Hertfordshire and Essex. The system serves 270 stations.
Pricing varies based on where you’re going and coming from. You can pay just for the trip you’re wanting to take, or you can get a variety of passes for travel, including day, week, and month passes.
London also has a variety of buses. Buses are easily the cheapest option for transportation. Personally, I found the buses to be incredibly confusing, but you can save a lot of money using buses to get to various tourist sites and such. Here’s more info related to maps, routes, and the types of buses found in London.
The National Rail operates throughout England and is often the fastest way between distant points (e.g. train from Northampton to London is about an hour, whereas by bus it will take about 1.5 hours). It is important to check the train schedule though for your journey; trains do NOT run 24 hours to some locations. Last train from London to Northampton typically leaves at midnight.
A good option for travel on public transport for visitors is the Oyster Card. This allows you to travel on the Tube, Buses, and Trains, and will calculate the lowest price for your journey automatically. You can order your Oyster Card before you leave, or you can get it at a station in England.
Taxis are also widely available, especially in London. However, taxis will likely be the most expensive option for public transportation. It can cut costs to share cabs when possible. Several taxis can carry up to 8 people. Tipping is also customary. Safety Point: in London, only the Black Cabs can be stopped by customers and pick up off the street. Even minicabs lined up outside pubs and clubs are breaking the law if they accept your fare without an advanced booking. Be careful of getting into a cab if the driver is flagging you, or walking up to an unmarked cab. These cabs may be operating illegally and charging unpredictable rates. Many clubs and businesses may have their own cab service; check to see if you can use their service.