I've tried to set up a personal Facebook account but it keeps blocking me out because it says I need to use my 'real name', but I am!! and it's a very ordinary British name. There are a lot of other people with the same name as mine on FB, so why can't I set up an a/c?
You may have changed your name multiple times or done some other suspicious activity. Try creating a new account.
Or else, in some automatted way which is basically used to target advertisements Facebook would have wrongly detected you to be belonging to some totally another country like srilank or china and so a British name is not getting accepted.
You need to use the following form to setup your account with the name that you desire https://www.facebook.com/help/contact/245617802141709 and will need to provide a scan of a government approved ID (such ad driving license, birth certificate etc)