Do not use the phrase "aviation medical" or anything similar with receptionist or GP. It is not a medical, you are signing to say you are fit to fly, the GP signs to confirm there is nothing in your medical records to prevent this.
The guidance documents were revised a few months ago and are now much easier for the GP to understand - make sure you have the up to date ones.
Remenber the standards required are roughly equivalent to those for driving. Private driving equals fit for solo flying, professional driving equals fit to carry passengers. So if you drove to the surgery you are fit enough for the GP to sign the form.
H
edit: yes thats the correct up to date form, but make sure you've understood it properly before you go