UK council-tax banding challenge check — neighbor-band cluster analysis against the free official VOA/SAA lookups, statutory route selection (formal proposal vs informal review, England/Wales/Scotland variants incl. the post-2023 Local Taxation Chamber), verified timelines (4/12-month decisions, 3/4-month appeals), evidence rules (the VOA rejects house-price-index data — verified), and the mandatory band-can-go-UP risk gate. Refunds backdate. No LLM.