I'm just changing the top strut mounts and I didn't follow what are you aligning with the hole??
The discussion is about the coil spring upper seat,
item 2 in this drawing.It fits into the rubber damper ring numbered 4 and together they sit on the top of the spring. However the upper seat's proper orientation is not immediately apparent.
Omega A/Carlton and Senator B use the same system. The Haynes manual for the Carlton says
"The small hole in the upper seat must be positioned on the opposite side of the steering knuckle (Fig 10.5)." That would be inboard when the strut is mounted on the car.
That would seem to be at variance with Doctor Gollum's findings posted above which has the larger drain hole inboard and the smaller hole outboard. Or have I misunderstood? Haynes Fig 10.5 is also ambiguous.
In your case I would make a paint mark on the upper seat relative to some known point before you compress the spring or disassemble the strut. You might find that there are already factory white and/or green paint marks. And it might well be that the Haynes manual has got the holes mixed up or maybe the holes are a red herring. Might be the factory paint marks that should be used for alignment.
Yours is LHD so if I was re-using the springs I'd put them back on the side they were originally fitted to. If you remove the struts, you'll need to get your suspension geometry checked and adjusted somewhere with the right equipment and that might be expensive. Hence it might be an opportunity to renew the springs.