Enquirer's five-year old daughter needed to use the toilet when they were in a shop so asked a member of staff if there was a toilet they could use. The shop's supervisor said this was not possible and that it isn't allowed for health and safety reasons. The enquirer had better luck in the shop next door.
This is not a health and safety issue. It is not unexpected that customers will ask if they can use the toilet in emergency situations especially if children are "caught short". Whether or not the outlet chooses to make the facility available to any/all customers is a matter of policy and discretion.