Here's a great bit of info from Govan Law Centre in Glasgow - it primarily applies to Scotland, however the guidance and pro forma can just as easily be applied in England and Wales as housing benefit is a UK wide benefit and can also apply as the arguments are just as valid anywhere in the UK.
Hope this helps.
http://govanlc.blogspot.co.uk/2013/04/launch-of-glc-toolkit-guide-calling-for.html