Rob , click on the link for my F2 restoration, i think on the first page of the thread you will see a picture of all my brake components dismantled
you will see that i managed to get my master cylinder apart, but it was really hard, first unscrew the plate inside then hold real tight and keep trying to twist it away, eventually it will break its seal with the large o ring, i also gave it a bit of help by trying to gently lever it with a stanley blade
Pete