Hi Reuben,
My undsterstanding of the uniform washing rebate is that you are given an allowance of £60 a year, of which you can claim the tax back on. So I understand it's about £12/year which would be £60 in total for 5 years. Someone else may know more.
Regarding council tax, what are the other houses in your street banded at? If they are all B (assuming identical type houses) then I think you may struggle to get it rebranded to A. Again I'm no expert but I did look into this previously