Mike - he was in 684 Sqn
Here is "Frederick Wills 1454360 Royal Air Force Volunteer Reserve, 684 Sqn" in the London Gazette 11 August 1944
https://www.thegazette.co.uk/London/issue/36649/supplement/3716/data.pdfand (this is for other people)
"WILLS, Frederick. 1454360 Flight Sergeant, No.684 Sqn.
L.G. 11/8/1944. Sorties 46, Flying hours 233.50. Navigator. Air2/9633.
Flight Sergeant Wills is Navigator to Warrant Officer Johnston*. His high standard of target finding and accuracy on photographic runs have in no small measure been responsible for the outstanding success of the crew.
Remarks by O.C., Wing.
Strongly recommended for the award of the Distinguished Flying Medal. Flight Sergeant Wills and Warrant Officer Johnston have done and are doing excellent sorties and they are a very keen and reliable crew.
Remarks by Air Commander, Eastern Air Command.
I concur in this recommendation. Flight Sergeant Wills has proved himself a capable Navigator on long-range reconnaissance flights and has carried out 46 missions in the course of the last eight months.
Tavender/Vol.II. K-Z. p.986."
1454360 Acting Flight Sergeant Frederick Thomas Baker Wills (His full name)(Navigator)
1376868 W/O James Aden JOHNSTON DFC RAFVR (DFC - LG: 11/8/1944:p.3715) (Pilot)
So all that remains is to find some type of war Diary and find out exactly where and what he was doing to get the DFM, when they were Flying out of Burma, Malaya and Thailand, photographing the Japanese activities. Although I suspect they were CONSTANTLY shot at by ground forces with dum dum bullets and enemy aircraft and that would be reason enough for awarding a DFO (after all their information they brought back was vital)
Don't forget they would have to fly low and slow to take the photographs (so they didn't blur) and then escape fire and aircraft as fast as possible. All that with no weapons to fight back on their mosquito!
*Good book to read "Mosquito Photo-Reconnaissance Units of World War 2 By Martin W. Bowman"