In relation to getting from the airport, here are the other options:
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Take the 200 bus from outside the arrivals lounge to the last stop of the M3/blue metro line, Köbánya Kispest. From here, take the metro to Deák Ferenc Tér, the junction of all three metro lines, where you should then change to the M1/yellow line and get off at Oktogon, two mins walk from your hotel. On each part of the journey, you would need to validate a transport ticket (230 HUF).
The Airport Minibus in the arrivals lounge costs 2,300 HUF single or 3,900 HUF return and will bring you to any address within the city limits. Call (+36 1) 296-8555 at least 24 hours before your return journey to arrange collection at your hotel.
A taxi from the only permissible operator, Zóna Taxi, typically costs 4,300 each way (fixed fare) but as Perplexed says, they're not that pleasant to use.
(€1 = approx. 250 HUF)
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