* state that the union intends to hold the ballot;
* specify the date which the union reasonably believes will be the opening day of the ballot; and
* contain such information in the union�s possession as would help the employer to make plans (for example, as appropriate, to enable him to warn his customers of the possibility of disruption so that they can make alternative arrangements or to take steps to ensure the health and safety of his employees or the public or to safeguard equipment which might otherwise suffer damage from being shut down or left without supervision) and bring information to the attention of those of his employees who it is reasonable for the union to believe (at that time) will be entitled to vote. In particular, the union must provide as a minimum any information which it possesses as to the number, category or workplace of the employees concerned. But a notice will not fail to satisfy the requirements simply because it does not name any employees."
The full Code can be found here:
http://www.dti.gov.uk/er/codiab.htm
Chris