try ringing the london number in ur emirates skywards booklet. i did and was surprised to be answered within one minute. i had the impression that the flight departures had to be between those dates.
flight sectors in either direction will accrue double points. flights where one sector qualifies but the other does not (for example london to dubai to bangkok), will give double points for the qualifying sector and single points for the non-qualifying one. u can claim if u've already booked.
answering my own question above, this offer can be booked through travel agents or the emirates website.
ian.