I have a btinternet account which I access through yahoo when on my laptop but on the ipad2 I connect through the mail at the bottom... However I am having a problem as it does not upload all of my emails on my iPad... Plus I cannot access any of my other folders... Any help on how to solve these problems would be great

Check your account help pages and see if they offer an IMAP server setup. If they only offer POP, then you can't sync folders.

To get more mail, check in two places. In the account settings (Settings > Mail, Contacts, Calendars, your account) see how many days back it is set to sync. That option may or may not be there. In the same place go to the Mail settings area and see how many emails you are set to Show. It can be as few as 50 or as many as 1000.

Also, when there are more emails in a folder than what are shown, at the very bottom of the email list (scroll down) there is usually a Load More option.