Do an svn switch and use the --relocate option:
http://svnbook.red-bean.com/en/1.5/svn.ref.svn.c.switch.html
(or in TortoiseSVN, right-click -> TortoiseSVN -> Relocate…)
The relocate does not require repository access and is meant exactly for the case where the content is the exact same but the repository base is changed.