If you're investigating something to do with planning or buildings, there's a very useful Guide to the Planning System at Planning Aid. The organisation provides planning advice to people who cannot afford expensive legal advice, so it's also a useful resource to bookmark if you ever need to ask a quick question about planning procedures.
Rather frustratingly, most of the useful information on the site is contained in PDFs, which means you cannot find specific information by searching for it. But as the service is provided by a network of volunteers, I'm going to volunteer my time to help address that. You might want to too.