Who did your instructional flight, and how could they not explain this to you? Very disappointing.
If you go to any flying club you're bound to find an examiner knocking about who can sign your licence. There's no fee, just a form which is one side of A4 to send to the CAA for notification.
Whopity, where's the reference for that, CAP 804? Haven't had chance to read it through yet.