G'day Karen,
In the book
The Sky Their Battlefield by Trevor Henshaw, there are 3 Marchant's.
The first Lt E.A. Marchant became a POW on 14 September 1918, after being shot down, but he was a gunner in a Handley Page Bomber, so I guess that rules him out.
The Second was a 2 Lt F.W.G Marchant who died of wounds 25 October 1916, so I guess that rules him out.
The last was a 2 Lt L.W. Marchant, who was a pilot of a DH9, he flew with 98 Squadron so he could be a possibility.
Hope this is of some help.
Regards,
Andrew