Here is Florida where the state flower is mildew we have long used paraformaldehyde powder to fumigate such things as leather goods. It used to be sold in small cloth bags as DiGas. It has been off the market for some years thanks to our EPA. However, you should be able to get some from a chemical supply company. This is the same chamical that is used in high contrast developers to produce half-tone negatives. Paraformaldehyde slowly releases formaldehyde gas. Place the camera in a ziplock bag with a spoonful of the powder wrapped in a piece of cloth and leave it for a few days. All the fungus and the spores should be killed.
For non-metallic objects such as books and leather goods take a tablespoon of copper sulfate crystals (bluestone is the common name) and dissolve it in a cup of water. Put the solution in a wide mouth jar. Take a cloth, an old wash cloth works very well and allow it to soak in the solution for an hour. Squeeze as much liquid out of the cloth as you can saving the liquid back into the jar. Save the jar and solution for later use. Allow the cloth to completely dry. Wipe the object with the dry cloth. This leaves an invisible coating of copper sulfate on the object and will not dicolor it. The copper ions with kill any fungus. When the cloth seems to be losing its effectiveness resoak it in the saved solution.
Fungus can also be destroyed by exposure to UV light. Strong sunlight can be used but this may be a problem in Britain. Remember fungus loves dampness and the dark. Hope this helps.