You can delete the state dropdown and replace it with a text field with the same name and change the default to UK for the country dropdown.
If you are only doing sales in the UK, then you can just manually update the options in the state dropdown and populate it with UK counties instead.
Express checkout requires a username, password, and access key.... it looks like you only have the username, and that username value is incorrect. It has to be API username, which is different than your regular paypal username. You have to get it from the API signature credentials area when logged into paypal.