Here is an app that we have found that may help:
This helpful app allows the user to plan their day out without the worry of being unable to find a suitable toilet. The nearest accessible toilet can be searched using the current location or a postcode. Pros: Location of toilets are shown on a map, and you can select a toilet to find further information about it, including the address, size of space, how to access, whether there is a hoist and the type of sling required. It tells you whether it meets the full changing spaces specification and if you require a radar key to access. Cons: Needs strong internet signal. The toilets are displayed on the map using colour coded pins signalling different types of toilets – you would need to use the app regularly to remember what each PIN stands for or flick between the index and map on the app.