We made our marmalade today as well
The recipe I use is dead easy - juice the oranges, collect the pips, put juice and water in pan, whizz up the rest of the orange and add to pot - put pips into a muslin bag and dangle in pot, bring to boil then simmer for 20 mins. Remove muslin bag of pips and squeeze to get all the pectin out. Then slowly add the sugar, dissolve and then bring to rolling boil for 25 mins.
Test for setting (plate in freezer, dollop of mixture on cold plate, let cool then draw finger through, if groove is left then marmalade is ready) put in sterilised jars - voila
2.5 kg seville orages, 4 kg sugar, 5 pints water
Makes about 16 jars