You can edit the URL of the repo that's used. We default to following
what the mirror list gives back because for most people, that increases
the usability of the network install _significantly_
Also, note that if your ISP has a local mirror, they should really
register their mirror[1] and say the netblocks they serve. Their users
will then end up getting their mirror by default and everyone can win.
The same can be true for people who have a static IP and a local,
private mirror -- put your IP into mirror manager and your local IP can
be given back.
Defaulting sanely is certainly good thing. However, the OP seems to
hit a problem when he is not able to change the URL from anaconda's
UI (whatever his reasons are). That would certainly be a bug,
wouldn't it?