Are you talking about your bath tub? We use a product called the works, you can buy it at any store and if you buy two or three bottles (they are only like a dollar a bottle), you take the liquid and pour it over every inch of your tub and let it sit for a few minutes. Then you rinse and it has gotten off everything. i love that stuff, no scrubbing or hard work.
If your problem is hard water, CLR spray will cut right thru it....it shines right up, too....when you rinse it.
Mr. Clean Magic Eraser is pretty good for getting rid of soapy film.
Is there any In uk ?