Someone on another forum has explained in legal language, that by challenging a council tax bill (contract of services), you can avoid paying it using Common Law.

Then he showed us this recent case
WIRRAL COUNCIL ? Admits that Council Tax is Unlawful and Sets a Legal Precedent. | www.tpuc.org
This bit is long, but well worth the read, brilliant stuff.
A DAY IN CWMBRAN MAGISTRATES COURT FOR COUNCIL TAX | www.tpuc.org