Mostly ok
5* for the concept behind the app, 3* for the app itself. The only thing I think really needs changing is the slide bar to select the cost of the car wash. It is way too sensitive in going up in penny increments so I found I could not get it accurate at all. + and - buttons that go up in 25p increments would be better or just let the user enter the amount themselves into £ and pence boxes. Other than that it’s a good concept and idea.