Having purchased some interior paint they claim that it should only
take one coat but after one coat, its clear that its going to need
two.

Now this is a light paint of a good white base yet there is no chance
one coat would do it.

So my question the paint they do that is actually called 'Once' I
think.......is that any better as I have heard some people say you
dont get away with one coat.

Anyone any experience of using it?

Thanks