"After the departing.... line up"

[VATCO]

Line-up Clearances

CAP 413:Line up instructions may be issued to more than one aircraft at different points on the same or crossing runways provided that:
a) it is during daylight hours;
b) all aircraft are continuously visible to the aerodrome controller;
c) all aircraft are on the same RTF frequency;
d) pilots are advised of the number of aircraft ahead in the departure sequence, and the position/runway from which these aircraft will depart;
e) the physical characteristics of the runway do not render preceding aircraft in the departure sequence invisible to succeeding aircraft on the same runway.
When line-up will take place at a position other than for a full-length runway departure the intermediate "Holding Point" designator shall be included in the line-up instruction.
Probably either of your scenarios could be correct and acceptable, depends as you say if you are happy with the prop wash etc.
I'm sure this thread will have some interesting debates though.