RAF Film Unit Mosquito DZ592. Which squadron?

[atckyrre]

ALong with a friend I am preparing an article for a Norwegian magazine covering Mosquitos in action over Norway during WW2.
DZ592 was one of these, apparently belonging to the "RAF Film Unit". It took part in several Coastal Command raids along the Norwegian coast and ended up being brought down by the blast from an exploding U-boot in Skagerak April 1945.
DZ592 was apparently built as a B Mk IV but was converted to a PR.IV.

Was RAF Film Unit an autonome unit or did it actually belong to a squadron? 540 Sqn comes to mind, since these seems to have been very much involved in PR-missions over Norway.
I have skimmed through Nesbit's "Eyes of the RAF" and all my Mosquito books without coming up with anything. So far I don't have any PR ORBs and in my references the highest DZ-serial in 540 Sqn is 517.

Any information, any leads will be much appreciated,

Kyrre