From Lorelle:

Luckily my uncle, John Tree kept a diary for 1943 which we still have and also we have quite a few of his letters that he wrote home. We also have found most of his service records so we have been able to piece much of his war story together to get a more complete picture of his war service. I think I am able to tell you where he was during that time in the paragraph below. 

My uncle John Tree voluntarily signed up to serve in the Royal Australian Air Force in 1942 in Brisbane, Queensland, Australia. After recruitment John was sent to the ITS (Initial Training School) at Sandgate, Queensland from 26th April till 20th July 1942. He was then posted to 3 WAGS (Wireless and Gunnery School) in Maryborough, Queensland from 21st July - 13 December 1942. John wanted to be a pilot but was assigned to be a gunner. On 6th January 1943 he was promoted to sergeant. From14  December  1942 -14 January 1943, John was posted to 1 BAGS (Bombing and Gunnery School) in Evans Head, New South Wales. From 15 January to 8 February 1943 he was moved to 3 ED (Embarkation Depot) Brighton (Sandgate), Queensland. From 10 February - 23 February 1943 he was posted to 2 ED (Embarkation Unit) at Bradfield Park, New South Wales. Then from 24 February - 5 March he was posted to 1 ED at Ascot Vale, Melbourne. Left for the U. K. on  the Nieuw Amsterdam 6 March 1943 via New Zealand and the United States. Boarded a train in San Francisco and went all the way across the country to Massachussetts then up to Halifax, Canada. Boarded a boat, the Pasteur, in Halifax, 8 April 1943 to sail to England. Arrived in Liverpool 17 April 1943. Took overnight train to Bournemouth. Assigned to 11 Personnel Dispatch and Reception Centre in Bournemouth from 18 April 1843 - 3 May 1943. Posted to No 19 O.T.U. (Operation Training Unit) Kinloss, Scotland from 4 May to 6 June 1943. On 12 May 1943 he was assigned to be a mid-upper gunner. It appears that they formed into crews on 18 May 1943. Mostly John stayed with the same men in his crew although there was a change or two. (Thomas McCash, the flight engineer who was killed the same day as John was flying for the first time with this crew that night.) In John's letters home he mentioned pilot Bill Simpson, bomb aimer Ron Pilgrim, navigator John Martin (also died that night) and wireless operator Bill Livesay.

Charlie Earnshaw completed the crew as flight engineer June 20th 1943. It also appears that they later picked up a rear gunner, F.S. Williams but he seems to be replaced by Clifford Reid. Rear Gunner, flight sergeant F.A. Fell joined the crew 14 January 1943 after Charlie Earnshaw left for some unknown reason. Seems that they had a hard time keeping a rear gunner.
I forgot to mention that from 20 July to 14 September 1943 John was posted to
61 squadron in Syerston, Nottinghamshire. There appeared to be a shake up in 61 squadron as they didn't fly for several weeks in September but John and his crew were reassigned to a Pathfinder squadron. They went to Pathfinder Force Navigation Training Unit (NTU) (RAF Upwood) 15 September - 24 September 1943. On 25 September 1943 till time of death, John was posted to
83 squadron Wyton, Cambridgeshire. 

I actually am getting a lot of the information from John's 1943 diary and his letters to home. One of my cousins Michael Tree has transcribed and notated the diary.
The following is a copy of part of one letter that he sent home dated 25 May 1943 that describes the crew that was formed at that time. It really humanizes them.
Dearest Mum and Family,
I am still in Kinloss in Scotland but will be leaving tomorrow for two weeks leave which I think I will spend in London and I might go with one of the boys (from the crew) to his place for a few days. Yes, we are crewed up now and I am with a great mob of chaps. They are all Englishmen and all sergeants. There are four Lancashire lads and a Welsh lad and I feel quite at home with them. I have had a few trips with them on the plane and have great confidence with them all especially the pilot who is a redhead and talks with a real Lancashire accent. The officer who gave him the test said he looked as rough as a diamond but was as firm as a rock and would make a very good pilot. Their names are Bill Simpson the pilot with a mop of uncombed red hair always sticking out from under his hat. Ron Pilgrim who is tall and dark and is classed as a very good bomb aimer. John Martin the Navigator who is always running late but always manages to get the correct course to get us back home. Bill Livesay the Wireless Operator is a little chap with a partly bald head of fair hair and a funny little giggle, we call him Willie the Wop. Then there is Cliff Reid, the Rear Gunner who is 19 and he is the one from Wales. So now you have it all and they really are a great mob. Of course I am the Mid Upper Gunner........                 Lorelle