RAF Servicing Commandos were, as the name suggests, servicing units with additional combat training. They were created to operate at the airfields right at the front line, either captured by the army or built by construction units, able to assist with their defence if attacked. Each Servicing Commando was around 150 men, a mix of the various technical disciplines (fitters, riggers, armourers etc.) sufficient to refuel, rearm and perform minor repairs on whichever aircraft landed at their airfield. Once the area was secure, and regular squadron ground personnel moved in, the Servicing Commando would move on to the next airfield.

The first Servicing Commandos were established for Operation Torch, the invasion of North Africa, and performed well there; further units (including 3207) were then created for Overlord, the invasion of Normandy. 3207 landed on D+1 (June 7th), though some of them were on a landing craft hit by an E-boat torpedo, most of those rescued and taken back to Britain. They weren't in France for long, returning to the UK to be redeployed to South East Asia in December 1944.

Your best bet for contacts would be [The Royal Air Force Servicing Commando and Tactical Supply Wing Association] (http://www.tswscdoassn.co.uk/), they have some members of 3207 listed on the "SC Members" page.

For general information there are a couple of articles about the Servicing Commandos in the Royal Air Force Historical Society Journal, the first in particular listing a couple of books and additional sources:
[No. 39] (https://www.rafmuseum.org.uk/documents/Research/RAF-Historical-Society-Journals/Journal-39.pdf)
[No. 51] (https://www.rafmuseum.org.uk/documents/research/RAF-Historical-Society-Journals/Journal-51.pdf)

There's also [a page about them on the Combined Operations site] (https://www.combinedops.com/ROYAL_AIR_SERVICING_COMMANDO.htm), including snippets from the diary of a 3207 Sergeant, and [a page on the Burma Star Association website] (https://www.burmastar.org.uk/stories/the-raf-servicing-commandos/) about their time in South East Asia.

There's an audio interview with a member of 3207 available [at the Imperial War Museum] (https://www.iwm.org.uk/collections/item/object/80012928), the SCU section starts in reel 3, and another member of the unit posted [an entry on the BBC People's War site] (http://www.bbc.co.uk/history/ww2peopleswar/stories/08/a2733608.shtml).

As /u/Vespertine says, you may also be able to obtain his records [from the government] (https://www.gov.uk/get-copy-military-service-records), and the Operations Record Book (ORB) of 3207 is held [at the National Archive] (http://discovery.nationalarchives.gov.uk/details/r/C7160307) if you're able to visit in person, or there are researchers who'll photograph it for a fee (e.g. ARCRE ).

This should not discourage further responses, but here is some info from the subreddit wiki, which may help: https://www.reddit.com/r/AskHistorians/wiki/militaryrecords#wiki_united_kingdom