heathrow airport (from terminal 3 to terminal 1)

Your best bet from terminal 3 to terminal 1 would be the heatrhow airport bus or airport train in between terminals.I am not sure how long it take?For more information you can go to www.yahoo.co.uk and seachring it from the search secetion.

P.S-Do not take heathrow express from terminal to other terminal,otherwise you would end up going to the center or Noeth London first than return to Haethow.Subsway won't be your best choice either.Because the subway is the circuit lane.

Hope this information can help you

by the terminal bus inside
takes about 45 mins

inside heathrow airport you can go from terminal 3 to terminal 1 by bus and it takes about 5 min.