Council tax rebanding query

A question about : Council tax rebanding query

Hope I am posting this in the right place. I'm looking at seeing if my home can be rebanded.Currently is the same band as neighbour's house which was identical at the time of being built in 1980. Both houses were semi-detached with attached garages and banded as C. The previous owner had 'my' garage knocked down and a third house built adjoining mine. My house is now a 3- bed mid terrace with no garage. As a consequence I can't work out a 1991 value since the house didn't exist in its current format. I understand that improvements can change banding but can 'UNimprovements' be used to reduce banding?

Best answers:

• Could still be a Band C, even with the unimprovements. Check bands of other similar type and size mid terrace 3 bed.
  Although house price indices are inaccurate, you could get a rough 1991 value using your purchase price.