I'm off to Homebase now to get some materials/tools. What for? Why, my own large format (strictly speaking multi-format) pinhole camera, of course!
I've got the design down on paper, and I'm pretty pleased with it. The only part which is looking slightly tricky is getting a tripod mount. I'm think I can just find a nut which has the same size thread as my tripod, and glue/bond it to the camera, but if anyone knows a more tidy/sturdy way, don't be a stranger!