I plan to come on hollidays in London. Can you tell me
how to go from Stansted Airport to Kings's Cross Station ?
what is the less expensive ?

National Express run coaches with fares starting from £7 single, for
more information see:
http://www.nationalexpress.com/desti...r&agentid=baa1

There is also a Stansted Express train service, taking 45 minutes to
Liverpool Street, this is £24 return, as long as you make the return
within a month. You can book online directly at
http://clkuk.tradedoubler.com/click?...891&g=12516031

For 6 days of tourism in London, what is the best travelcard
to buy ? what is the price approximately ?

If it's just for yourself, & you're a tourist you'll probably not need
to go outside of Zone 3, a 7 day travelcard Zones 1-3 is £25.
--
Joe Patrick
Railways Online - for GB railway news, information & photos
http://www.railwaysonline.co.uk