Think laterally. What about buddleia, alternating with holly? The
former is very fast and can be pruned ad lib as the holly grows.
It may not be evergreen, but isn't bare for long, and grows to 20'
or so.

I can't guarantee it will love acid soil (though it seems to grow
everywhere), but holly certainly likes it. And holly isn't a very
slow grower. People with acid soils may be able to think of an
alternative to buddleia.

It is a mistake to try to combine permanence with quick establishment.
Plants don't grow like that.


Regards,
Nick Maclaren.