Oh Peter, I LOVE orange marmalade!
For a couple of weeks in February the shops have boxes of Seville oranges from Spain for marmalade making.
We buy and freeze them whole so during the year as we run out we can make a fresh batch of marmalade.
Another time saver is, after defrosting them, to halve then boil them before slicing the peels and removing the pips. Makes it much easier to slice the peel as its very soft by them. Then make the jam.