Well seems that they may of released it slightly earlier than the announced 22nd of October as mine arrived this morning.
There is apparently a work around to 'upgrade' Windows 7 release candidate to another version, namely Home Premium in my case.
I'm about to embark on this adventure following tips from here: http://icrontic.com/articles/upgrade-the-windows-7-rc-to-retail
I'll let you know how I get on :)