Out of all the four flights from LHR, only CX252 is showing a 74A seat map.
From EF:
CX252
LHR 10/26/07 12:45 PM
HKG 10/27/07 7:25 AM
F4 A2 J6 C3 D0 I0 Y9 B9 H9 K9 M9 L0 V9 S0 N0 Q0 O0
Beware, of course, of last minute aircraft subs.
Hope this helps.