Removing users in WordPress 2.0

Removing users has been covered quite a lot in the past but not when using WordPress 2.0 and users having roles.
It has been mentioned that by reducing a user to ‘0’ they can then be deleted.

My problem is that there is no ‘Delete checked user’ option and at the same time I cannot add any more users to the blog.

I would like to delete one user added earlier by accident and also add two more students to the blog, my new untested blog is at https://www.stbeesprimaryschool.ethink.org.uk and my attempt to make things clearer are here:-

https://www.chocolatebones.co.uk/user_options.doc

Would I be better starting again and adding a WordPress blog to my own server space??

Any help at all much appreciated, have trawlled all the help forums but cannot find anything that I either understand or answers my questions directl

Cheers
Kevandali