You asked about legal requirements. The relevant legal frameworks are the Health and Safety at Work Act and the Workplace (Health and Safety and Welfare) Regulations 1992.
The HSWA requires employers to ensure the health and safety of all employees and
anyone who may be affected by their work, and to maintain the workplace
and/or premises in a safe condition, which includes adequate cleaning. However it is rather short on specifics.
The latter Act is liable to be more fruitful in terms of specifics. See here - applies only in England and Wales.
http://www.opsi.gov.u...ksi_19923004_en_1.htm
You are still going to be better off timewise challenging the boss directly having armed yourselves with a little knowledge of the legislation - which would indicate your seriousness at escalating this to the statutory authority if he doesn't get it sorted fast. Talking to the H&S people and getting them to shift quickly will take forever unless life or limb is at stake.