The relevant regulations are the Personal Protective Equipment at Work Regulations 1992.
Regulation 4 states:
Every employer shall ensure that suitable personal protective equipment is provided to his employees who may be exposed to a risk to their health or safety while at work except where and to the extent that such risk has been adequately controlled by other means which are equally or more effective.
The accompanying guidance states:
Employers should, therefore, provide appropriate personal protective equipment (PPE) and training in its usage to their employees wherever there is a risk to health and safety that cannot be adequately controlled by other means.
In order to provide PPE for their employees, employers must do more than simply have the equipment on the premises. The employees must have the equipment readily available, or at the very least have clear instructions on where they can obtain it.
You may find this useful reading http://www.hse.gov.uk/pubns/indg174.pdf