Father Jack, I suspect that most of the 777s you're dealing with are -200s if the pilots are making the "180k to 8, 160k to 4" request of you, and no, I don't think they're trying you on. That's a comfortable profile for a -200, if just a little tight maintaining 160k to 4. (In Cat II/III conditions, ideally, they'd probably like to be back at ~140k by 6nm [and ~150k for a -300] to allow for a properly stabilised approach below 1500'.)
However, if it's a heavy -300, 170k to 6nm would be ideal (if you're wanting things kept tight), to save having to get the gear out too early with all the associated extra noise and unnecessary extra fuel burn. A -300, close to MLW, (as we usually are when landing at Heathrow), can't go much below ~167k without taking 30 flap, for which we have to have the gear down.
Hope this helps.
[This message has been edited by 410 (edited 27 April 2001).]