Managing iCloud Drive and Photos space on iPhone

Hi,

I use both iCloud Photo Library and iCloud Drive. iCloud Photo Library is set to 'Optimise iPhone Storage'.

iCloud Drive

Once I've downloaded a 2GB file in the iCloud Drive app (iOS 9) I can see my free space has dropped by 2GB in Settings → General → Storage

I cannot see any way to remove that 2GB from my iPhone (only to delete it entirely from iCloud Drive).

iCloud Photo Library

If I view/download a 2GB video from my iCloud Photo Library I can see my free space has dropped by 2GB in Settings → General → Storage

I cannot see any way to remove/free-up that 2GB from my iPhone.

Questions

1) Is it possible to remove the 2GB file from my iPhone but NOT from iCloud Drive?

2) Is it possible to remove/free-up the 2GB video from my iPhone but NOT from iCloud Photo Library?

My guess is that there's no way to manage this manually and that you have to trust iOS to start off-loading these files as the iPhone gets close to filling-up.

Thanks for any help,

Dave