I tried to lower my band as I checked these websites and there was a mix of bands between the area.
I was a band B, but some around were A's and C's.
I tried and failed as said I was right.
However it didn't cost me anything and only took 5 mins to do so worth a go.
All they do is send you a questionnaire to fill out and you return it.
You just answer questions about the property and thats it!
They then wrote to me to keep me informed, then eventually letter came through to say been unsuccessful.
They said I could appeal it, but gave me explanation of why, so I felt that was ok.
Main reason was as it was over so many square feet.
So the number of bedrooms and size come right into it!
As well as area you live in.
Just get in touch and see what they can do.
it's all free and worth a try as could save you money.
I do admit C sounds alot but maybe in good area?