Services by geo fenced area

Hi all
I am new in bubble and what I want achieve is as follows
I need to create an app, where services can be bought by user.
The services will be provided in a area for example London only , but in future the services will expand in another area.
How do we handle the logic in the app that if user ask for the services from outside the area (london), then the app should tell the user that the services user is looking in their area is not available right now. but please submit the form and we can collect data to notify user in future when we start selling service in the required area.

Thanks in advance

sanjay

You could do this by getting the distance to something.

Ex: If Current Location Distance to London’s Center is < 20 miles : Approved
If Current Location Distance to London’s Center is >20 miles : Denied