I finally got the the workshop room for the optical equipment cleared away, and am a little disappointed by how much I underestimated the size of my projector.
The room is actually 4 x 5m, which I had thought would be quite large enough for this purpose, but looking at it with the projector against the 4m wall I am no longer so sure.
The projector is an Isoma M119G. Small bit of Swiss machine tool trivia: ISOMA is an acronym for Instruments Scientifiques Opitques Microscopes Appareils.