Q: Deleting iCloud backup and storage

Hi,

Can anyone advise me on whether deleting past backups on previous phones which still appear in my "storage & backup" will delete any past information on my current phone's backups? 

My iCloud storage is full so I need to free some space.  2 old back ups from 2 previous phones (iphone3 and 4) appear in my settings/icloud/storage and backup/manage storage.  If I delete them will this free up some space?  Will I lose any data by doing this?  My new iphone 5 would pick up where my last phones back up (if you know what I mean).

Any help would be greatly received.