I recommend to take the public bus in order to reach the hotels around LHR. The public buses are free of charge and are much more reliable than the Hoppa bus. See
this thread for a discussion about the public buses. The thread contains a link from Sprout informing about the location of the hotels and the bus routes. Bus 555/556/557 goes from T4 to the Marriott. It's a 1-2min walk from the bus station to the Marriott. Just ask the driver about the Marriott and he will tell you at the bus stop to exit the bus.
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Short overview: KLM FD, LH M&M
[This message has been edited by LH738 (edited 10-25-2003).]