It is free to check and challenge your Council Tax band, the bands are set and maintained by the Valuation Office Agency. You can do so using the above link or alternatively by calling 03000 501501 during office hours for the best advice before signing with an outside Company.
Council Tax is paid over a maximum of 12 months of the year. If you are up to date with payments and your account is not in debit you will pay council tax from April to March every year.
Council Tax Amounts 2018 to 2019