Council Tax Band Challenge

HollySummer

I'm currently in the process of challenging my mother's council tax band (Authority to Act form completed). She purchased the property in 1984 and I have all the documentation relating to the purchase including the valuation at that time. The property was recently valued and the estate agent expressed surprise the current council tax banding was as high as it is, hence my proposal.

I'm using guidance from this site and the gov.uk site. Results from the valuation check and Nationwide's Valuation Check and House price calculator suggests I have a case. However, looking at the gov.uk guidance, neither of these can be used as evidence.

That leaves me with providing five addresses of similar properties (bungalows) who are already in a band lower than my mothers. I've done the best can with this as no two bungalows in the road or nearby are the same. The gov.uk site cites 'Evidence From House Prices' is acceptable if dates for sales were between 1st April 1989 and 31st March 1993 (confusingly it then provides a link to where property sales prices online can be seen 'from 1995 onwards'. Unfortunately, none of the other properties were sold during these times so I am unable to use this option.

This appears to leave me with little evidence other than the addresses of the five other properties or does it? Has anyone else found themselves in this position and if so, did you manage to get anything else accepted as evidence (the estate agent has provided documentation to with regard to the recent valuation).