If you work for an agency, then there might be a few complications as to your employment status. Just telling someone that they are "stood down" is not legal in todays employment laws.
Your local Jobcentre Plus should have advisor's who should deal with this matter for you. The reason why I give this suggestion, is because I knew of a similar incident that someone was informed by their boss "that work would not be available every day". The person began to get into debt, sought advice from the Jobcentre and CAB, and the boss was made to comply with the law- 'Pay the person or Sack them'
My contracted hours are 45pw. There is nothing in the T&C that state I will NOT get paid if laid off. I took the Directgov info to the bosses this morning and their faces dropped when they read it (literally).
Later, one of them told me informaly that they had been given wrong information from the head office. He also said the lay-off is being reconsidered.