MWeb is SAIX. and you don't need to be registered at that site to connect to the news servers..
All you'd need to do is get a usenet client (like grabit) and configure it to use the saix news server (news.saix.co.za). The SAIX news server is really cool in that allows you to download uncached things at decent speeds after 6PM until some time early in the morning (7 or so), so you can get your NZBs from anywhere.
BTW, why MWeb? They're pretty much the most expensive ISP around.