I do think its the plastic packaging that makes the bread sweat, it was better years ago in the waxed paper. I now keep bread in the freezer and take a few slices out as and when I need it.
I bought a small Kingsmill 50/50 sliced loaf on Tuesday, dated 12 June. This usually lasts for at least a week, sometimes two, in the bread bin. Last week and this I have found it to be mouldy next day. I suspect it is due to the awful wet weather conditions. Has anyone else experienced this?