great, thanks for that, will let you know how it goes...
I chose cancel redirect in dreamhost panel and from there it decided it wanted to cancel the website from being fully hosted
So I've told it to be fully hosted again and have re-inserted the redirect, not sure why, guess I forgot what I was trying to do!
I've uploaded the .htaccess file to old.org via ftp, it says the upload was successful but I can't see it in the directory listing so guess it must be hidden.
So old.org redirected to new.com as before but now old.org/Main/aPage failed to do anything. So I've taken the redirect off again (which made dreamhost want to take the whole thing down again) and re-chose to make it fully hosted.
Will let you know what happens next!
Thanks for the help