Valuation Office Agency
An actual change to the locality might be the start of scheme works or some other change associated with a scheme which makes a physical difference to the locality. If the scheme is approved by Parliament it is likely to be some time before things happen on the ground. When physical changes do occur a review of Council Tax bands may be appropriate.
The law currently only allows compensation for planning blight to be sought from the authority proposing a scheme under the Land Compensation rules, which is nothing to do with Council Tax legislation. You may wish to contact the Department of Transport direct for further information about the HS2 rail link, for example, or the local authority responsible for the scheme.
For Council Tax queries, the Valuation Office Agency can deal with your enquiry. There is no charge for this service. Find the contact details of your regional VOA office here.