Im logged in as myself....but for some strange reason when I send an email my user name has been change to a different name with my email address in brackets beside it.....e.g. 'joebloggs' (mynamegmail.com). Whats even weirder is that my replacement name is one of my friends names but she dosent even have a Gmail account!! How do I fix it?? Any help much appreciated!

Go to Settings -> Accounts and look at the "Send mail as:" section. You will probably need to edit your sender information (click the "edit info" link).

Thanks you so much!