If you do not want to pay for two seperate transport rides (350 HUF each ride/ticket), you can buy a Transfer Ticket (530 HUF) valid for two rides between metro trains, buses, trams and so on.
Your first trip is valid for 100 minutes and your second trip (the transfer) is valid for 80 minutes, but your transfer must be taken within the first 100 minutes. See the BKK Transport T&Cs.
On this web page you will find detailed travel information about the various transport methods you can use when travelling from London (UK) to Budapest International Airport (Hungary). Here you should be thinking about your flight and more importantly which airline to use in terms of expense and route. The web page that follows this one will then give details of how to get from Budapest International Airport to Budapest City.
If you are not aware of the budget airline called WizzAir WebsiteWizzAir it is fast becoming the cheap alternative to RyanAir WebsiteRyanAir. WizzAir flights to leave from London-Luton Airport only whereas RyanAir flights leave from London-Stansted Airport only. Either way, both airlines are way cheaper than British Airways WebsiteBritish Airways, whose flights leave from London-Heathrow Airport (Terminal 3) only. Getting to a particular airport, from Central London, is quite easy.
In the case of travelling to London-Luton Airport WebsiteLondon-Luton Airport it means buying a National Rail THROUGH Ticket (from a Central London Rail Station or Online) that allows you to take a train from London's St. Pancrais International Station (or Farringdon Station) for example to London-Luton Parkway Station. Farringdon Station is less crowded/busy/annoying than St. Pancrais International, so I would recommend using it instead.
A train ticket to London-Luton Airport (UK)
Rail ticket prices vary, depending on which train operator you use, but a Return Open-Ticket for one adult is currently Thameslink Railway Website£24.90 - with Thameslink Railway. A Single Open-Ticket is £14.20. If you want cheaper you might want to try the train price comparison website called The Trainline WebsiteThe Train Line. And do not forget that if you book in advance many train operators will normally offer great discounts.
Upon arrival at London-Luton Parkway Station you then have to take a 10 Minute shuttle bus ride to the actual London-Luton Airport terminal. The shuttle bus fare is currently £2.10, but this will be included in the price of your Nation Rail THROUGH Ticket. If you forget to buy a THROUGH Ticket, for whatever reason(s), and therefore have a standard train ticket to London-Luton Parkway Station only you can always pay the £2.10 fare when you get on the shuttle bus.
With Stansted Airport WebsiteStansted Airport you need to take a National Rail train, known as the Stansted Express WebsiteStansted Express, from London's Liverpool Street Rail Station to Stansted Airport. A single person, return open-ticket, is Standard Express Fares Web Page£28 (purchased on the day), however, you can get that down to £14 if you Standard Express Special Offers Web PageBook In Advance. Note: The Stansted Express train does not use a particular platform, so it is up to you to check which platform it will use on your particular day of travel.
Liverpool Street also has a Tube (Underground Train) Station of the same name, located within the rail station, so if you are travelling to Liverpool Street Rail Station by tube train you need to take either a Hammersmith & City (Pink) Line, Metropolitan (Burgundy) Line, Circle (Yellow) Line or Central (Red) Line tube train and get off at the station called Liverpool Street where upon exit of that tube station you will see the National Rail station platforms.
You can DRAG THE TUBE MAP or SEARCH FOR A STATION
Buses are not a problem as many bus routes go to Liverpool Street Rail/Tube Station, coming from all directions of central and outer-central London, such as the 11, 23, 26, 35, 42 and 205. Here are the Official Bus Numbers & Routes Web PageOfficial Bus Numbers/Routes from London Transport.
If you are flying with British Airways you will need to travel to Heathrow Airport WebsiteHeathrow Airport (Terminal 3), located in Greater (Outer) London. You can get there by taking a Piccadilly (Blue) Line tube train to the tube station called Heathrow Terminal 3 (which is Heathrow Airport) - This will cost each adult Single Fare Finder Web Page£6 Cash (Travel Anytime), £5.10 Oyster Card (Peak Times - Monday to Friday from 0630 to 0930 and from 1600 to 1900) or £3.10 Oyster Card (Off Peak - At all other times including public holidays).
Taking a Piccadilly Line tube train from Leicester Square tube station (Central London) for example, to Heathrow Terminal 3, normally takes between 45 Minutes and 1 Hour. However, even though the tube trains are normally very frequent and very reliable delays can still happen, for whatever reason(s), so always give yourself 90 Minutes journey time just to play safe.
As an alternative you can take the National Rail train called Heathrow Express WebsiteHeathrow Express from Paddington Rail Station, located in Central London, to Heathrow Airport (Terminal 3). A Heathrow Express fare will cost each adult Heathrow Express Fares Web Page£27 (Single) or £42 (Return) whereas an Express Saver fare will cost £22 (Single) or £37 (Return).
Gatwick Airport, just like Heathrow Airport, has a dedicated train going to it called the Gatwick Express WebsiteGatwick Express. It travels from London's Victoria Rail Station to Gatwick Airport in approximately 30 Minutes and currently costs each adult Gatwick Express Fares Web Page£17.80 (Single/One-Way) and £31.60 (Return). Trains are approximately every 15 Minutes.
You can get to Victoria Rail Station by taking a Victoria (Light Blue) Line tube train to the tube station called Victoria Station. Upon exit of that tube station you will either be standing inside, or just outside, the rail station called Victoria. You cannot miss it because it is one of London's main terminal stations.
The airline called EasyJet WebsiteEasy Jet goes to Budapest, leaving from Gatwick Airport or London-Luton Airport, but their airfares tend to be a little expensive. They do have great offers sometimes (i.e. £80) but you need to watch out for them, otherwise you are looking at an average priced return trip of £140+ per passenger.
Travelling to an airport by National Express Coach WebsiteNational Express Coach these days is still far cheaper than using the above mentioned transport options. However, the trouble with travelling by Coach (or Bus or Taxi for that matter) is the risk of a longer journey due to very possible Traffic Jams and Motorway Accidents.
To travel from London Victoria Coach Station to Heathrow Airport (Terminal 3) using National Express is currently £6 plus £1 Booking Fee and usually takes around 45 Minutes to arrive at Heathrow Airport. Sounds great, even when optional luggage and travel offers are taken into consideration (i.e. £8 for 1 Extra Bag), but the reality is you still need to travel to Victoria Coach Station for example whereas with a tube train you can use any tube station to start your journey to Farringdon Station or Heathrow Terminal 3.
If you are travelling to Stansted Airport, you can take the A9 National Express coach from Victoria Coach Station, Liverpool Street Tube Station or Stratford Tube Station. The fare from Stratford Tube Station is £10 (one way) or £15 (return).
Below is an actual time recording from London-Luton Airport (UK) to Budapest International Airport (Hungary). This route was quite long because of the time gaps (waiting times) between each type of transport journey. Furthermore, the train to London-Luton Airport was not working so I was forced to take the National Express Coach instead:
Normally the above journey (UK to Budapest Airport) takes around 4 Hours 54 Minutes, but in this case because of the National Express coach and coming from Stratford (as opposed to coming from my normal apartment that is much closer to Farringdon train station) the journey time took 7 Hours 54 Minutes. An extra 3 Hours, wasted. Timing is important!!
Below is an actual time recording from London-Stansted Airport (UK) to Budapest International Airport (Hungary). Although there was a 15 minute delay with the aeroplane, this route took a standard length of time:
Hopefully the above methods of transport give you a better idea for planning your journey/route, in terms of options for getting to your chosen airport. More information about each transport operator and their prices can be found by following (clicking on) the BLUE words (links) above.