Of almost any destination in the world, flying into England, if your documents are in order, is one of the most effortless undertakings in global travel. There are no shots to get, no particular safety precautions, no unusual aspects of planning a trip. With your passport, airline ticket, and enough money, you just go. In general, if you're not bringing any illegal item into the British Isles, Customs officials are courteous and will speed you on your way into their country.
Of course, before you lift off the ground in your native country, you can do some advance preparation. That could mean checking to see if your passport is up to date (or obtaining one if you don't already possess one), or taking care of your health needs before you go, including medication. In the case of London, you might want to make reservations at some highly acclaimed restaurants or even buy tickets in advance to hit plays in London's West End.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.