Ive searched the FAQ's and posts to see how to do this, and see where I am supposed to change my user name. My problem is there is no cursor in the box to type a new one or to add anything, am I doing it correctly or being utterly dim? I thought it could be a browser issue, so tried multiple browsers, all had the same issue. All I have under My Mumsnet is settings, which is where I found the account information with what appears to be where I change my username. The box for changing my email address works fine, so does the password box to save changes, its just the username one as no cursor, but I cannot see where else to change my username, so you can see why I am completely stumped...either that, or completely dim. 
Thanks for the help.