Changing group permissions in Sharepoint services

[Chrispy]

The temp. in my room has just topped 30°C and my brain's fried but...

 

I want to change the group permissions in Sharepoint to allow users to add document libraries (specifically surveys) but don't want to override the current permissions that are basically contributor level but without 'delete items' rights.

 

Any ideas? (in easy language please, I'm struggling!)

Chris