Help! Dynamic lighting is trying to build?

ive got a persistant streaming level with a landscape, and another streaming level with dynamic skylight and directional light.

Then another few levels that sit on the landscape, some of those have stationaty and static lights, but those lights are only in the levels themselves not the pesistant or landscape level.

In the levels window, i make only the dynamic lighting level and land scape visible, and click build, and it tries to take forver to ‘build lighting’? Does anyone know whats going on?
The interface suggests only visible levels are built? So if the visible levels have dynamic ligting only, dynamic skylight, whats going on? Do skylights ‘build’ even if dynamic? Does unreal try to build lights that are not visibile?

Cheers

Hi just deleted all skylights to see what would happen and after doing so the level seems to still build skylight radiosity in build?! Some answers would be great, thanks