How to get there? If you start from some distant country and are not a big fan of railways or buses, you can still go by plane. Of course, if you are already in, for example, Paris or Brussels, you can also consider the train. London is served by the following airports: Heathrow, Gatwick, Stansted, London City, Luton and Southend. Prefer direct flights. A lot of nerves are saved. If you choose a flight ticket based on the price, it is also worth considering the cost of ground transportation. Because it is worth buying a city transport card anyway (either Travelcard or Oyster), then Heathrow and London City are connected to the Underground (or DLR) network. Other airports are further away and you have to factor in an extra cost of a couple of pounds to get into and out of the city. Therefore, a cheaper flight ticket can be even more costly. You now have to have a passport, even from EU countries. The country has never joined the Schengen area. Therefore, a careful document check is carried out not only when boarding the plane, but also when leaving it. You may (or may not...) be asked questions about the purpose of the trip, the duration, the hotel and the amount of money you are carrying.
The largest of London's airports. 24 km west of the centre. All terminals are connected to the Underground network, the journey to the city centre takes 45 minutes. At night, when the Underground is not working, night buses N9 run every half hour in front of each terminal. The gates of this terminal are actually located in three buildings. The main building is A, where baggage operations, security checks, etc. take place. B and C are smaller replicas of the big building and are quite far away. So, don't be surprised if, when you get off the plane, there are no document checks, customs and luggage collection waiting for you right away, but instead you have to get into the "mini underground" car and go somewhere. You can get a little idea of the size of the airport in the following video .
40 km south. Victoria Station can be reached in 30 minutes by train. Gatwick has one runway but two airport buildings. The main one, the southernmost one, has a connection with the railway. It is connected to the second station by free driverless buses running on the flyover. Or are they mini-trains ... The ride is short, but interesting. As a note, "gatwick" means goat farm in the archaic language.
80 km north-east. The Stanstead Express train (directly from the tunnel under the airport) to Liverpool Street station takes 47 minutes. But if you get off halfway at Tottenham Hale Station and take the Underground (Victoria Line), you will get there faster.
10 km east of the centre. Right next to the airport exit is the DLR (Docklands Light Railway) station. From there you can go directly to Bank (and Tower Gateway) stations, where you can transfer to several Underground lines. The airport is very close to the city centre, so it is used by many businessmen. But, honestly, the airport building looks like a slightly converted vegetable warehouse. Compared to Tallinn Airport, which is really beautiful, it's like comparing Mercedes to Trabant. :-) It is planned to liquidate this airport in the coming years.
45 km north-west. Shuttle bus Youtube to Parkway train station. From there take the Capital Connection train to King's Cross station. The duration of the ride is 30 to 45 minutes.
68 km to the east. It is unlikely that you will get there. Connection with railway trains.