Jan, I read the article by Nils M, of IPMS Stockholm, where he described the camouflage and other details. He claims that the information discovered in recent years (i.e., up to 1999), has disproven the previous assumptions re the BOAC Mosquito fleet colours. Although I have no reason to doubt him, or his research, the use of the 'Fleet Air Arm' type colours seems a strange choice, and I can think of no reason why it should be so, other than to, perhaps, give the Mossies a different appearance to those of Coastal, Bomber Commands etc. The Mosquito B MkIV used by BOAC I know to have been in 'standard' upper cam, with 'silver' undersides, and a photo I saw of one of the MkVI's some years ago, seemed similar in tones in the B&W pic. However, the research and facts presented by Nils of IPMS seem to point to the scheme portrayed, so, I'd go for that.
BTW, when you get around to finishing off the filled-in cannon ports, it's almost certain that these would have been blanked -off in the same way as the TIII trainer version's. They had blanking covers of thin aluminium sheet, the same shape/profile as the 'troughs', only larger all round by a little bit, say 10mm or thereabouts, fitted over the depressions of the troughs. These were flush with the surrounding fuselage contours, and held in place by screws (possibly glued also), the latter being virtually invisible under a coat of paint, the same colour as the under surface. Easiest way to replicate these in 1/48th scale is to either scribe them in, or add them from thin paper or thin plastic card. They were just visible as an outline. I've got some close-up shots I took of these on the now lost BAe TIII, but they're on transparency, along with shots of the internals of the cannon bay and bomb bay. There is also a small viewing hatch, looking from the cockpit, into the bomb bay, roughly in line with the front bay bulkhead, behind the nav's position,central to the mid-point of the spar and bay. If it's too late to replicate this, forget it, it probably wouldn't be seen through the cockpit canopy anyway, in this scale!