When I was a child my mother would always make marmalade at this time of the year. It was such a bonus for us to get such a glut of fruit in the middle of the winter.
My mothers goal was to make well behaved marmalade that set properly. She rarely achieved this goal. Each year there were new tips and pieces of advice played around with. Put all the pips in a muslin bag and steep this in the marmalade. Next year, include a chopped up grapefuit - they are full of pectin. Next year, include a chopped up lemon - they are full of pectin. But nothing seemed to work.
So, till this day, homemade marmalade, in my opinion, should be quite runny. This is my frame of reference. This is what I know.
I presume nobody needs a recipe for marmalade but for the record I like to put a slosh of gin in at the end - this adds a lovely zing to the marmalade and helps make sure it doesn't set too much!
Don't add the hooch too early or all the alcohol will evaporate. You need a bit of a kick to it.
Serving suggestion - serve on some lightly buttered, fairly well burnt toast.