When Seville oranges are in season make this traditional marmalade. They're more bitter than other oranges and are perfect for this.
BUT, what do you mean by "brown sugar" - there are many types. I made it with muscovada (not being an expert cook, but presumably you want to attract such as me?) which makes it very very dark, but still great, What do you mean by setting point? If I'd left it boiling for 2 hours it would have almost boiled dry. One hour reduces by 50% on gentle simmer. But worst of all, how didn't you notce that the combined capacity of the 3 jars you specify is less than the weight of sugar in the recipe? Almost had me panicking (when that 3* 240g got thru my thick skull that your sugar weight was wrong. A 770g pile of sugar is a frightening sight - especially thinking that i would probably, if successful, eat the lot in three weeks! Got a recipe for honey? - 21 Sep 2014 (Review from Allrecipes UK & Ireland)