I do not believe that you would need separate toilets or changing areas for visitors and staff, both visitors and staff must follow the same procedures of hygiene anyway.
Also, if you are operating a high-care and low-care area then i would guess that you would also have two sets of PPE?
4.8.5 in the BRC standard states:
Where an operation includes a high-care area, personnel shall enter via a specially designated changing facility with arrangements to ensure that protective clothing will not be contaminated before entry to the high-care area. This shall incorporate the following requirements:
· Clear instructions for the order of changing into and out of dedicated protective clothes to prevent the contamination of clean clothing.
· Site-provided footwear shall not be worn outside the factory.
· Protective clothing shall be visually distinctive from that worn in lower risk areas and shall not be worn outside of the high-care area.
· Hand-washing during the changing procedure shall be incorporated to prevent contamination of the clean protective clothing.
· On entry to high-care areas, hand-washing and disinfection shall be provided and used.
There shall be an effective control of footwear to prevent the introduction of pathogens into high-care areas. This may be by a controlled change of footwear before entering the area or by the use of controlled and managed boot-wash facilities.
I hope this helps.