Freedom of information, what a wonderful phrase...(now sing to the tune of The Lion King's Hakuna Matata) - well it nearly works!
I'm always going on about online sources of information, and if you know where to look you can find out nearly anything you want - and for free. I've talked before about getting access to Land Registry data on actual sold house prices and although Land Registry will charge for a report, sites like nethouseprices will display them for nothing.
Another useful information source is the Council Tax Valuation List where you can instantly find your council tax band online. I know i know many people will know it, especially if it's your main home, but it may save a few people rummaging around looking for council tax statements.
You'll need this information to complete your PIQ (Property Information Questionaire) which is part of an pre-requisite to, a Home Information Pack (HIP).
Another question you'll have to answer is whether your house has flooded since you've owned it - the last PIQ form I saw also asked if you'd checked the Environment Agency website to check if you're at risk of flooding, interesting but luckily I was not.