Isn't that really early for Seville oranges? Usually it's end of January through to mid-February...
I use a pre-war (1930s) method for making marmalade. No need to worry about pectin or pips. Here is what I do:
https://www.cyclechat.net/threads/recipe-reynards-easy-peasy-lemon-squeezy-marmalade.256471/
The only difference to this (since I originally posted this four years ago) is that I now soak the cut fruit overnight in the water (between steps 6 and 7) as it gives a softer result when cooked. With a 1-1 ratio of sugar to fruit, you get a lovely zingy flavour and a really good set without any messing around.
P.S. If you still have any cranberries left (fresh or frozen), cranberry & orange marmalade is lush. Use one part cranberry to one part sweet oranges or tangerines. Trust me on this one.