The Health and Safety (Safety Signs and Signals) Regulations 1996 details that Prohibition signs must be displayed to prohibit dangerous behaviour, access to certain areas and types of behaviour.
Prohibition signs must have a black pictogram encircled by a red band and then dissected by a red diagonal bar – the red must form 35% of the sign.
Choose from 2 quality materials. Self adhesive vinyl is a flexible material ideal for use on any smooth, indoor surface. Rigid plastic measures 1.5mm thick for extra durability (fixings required).
If the standard signs available don't convey your message, have you considered DIY signs printed in house?