Apologies for lateness of reply...
Last year i took
@flossietoo 's advice and made blackberry brandy - like every year, i thought i should make some sort of note of the 'recipe' i'd followed for future reference, and like every year i failed to do so - and i was rather hoping she might butt in on the recipe front.
Pretty sure it was 4oz. of sugar to 1lb. of blackberries to a bottle (70cl.) of brandy - i steep mine in a 1l. kilner jar, which fits it all cosily.
I'm a big believer in letting the fruit bleed into the sugar for a day or two before adding the liquid, and with the blackberries i think this is even more important as you can 'crush' the fruit a bit by shaking them up in the jar with the sugar acting as the abrasive.
Once the liquid is added, you'll need to agitate the contents over the course of a day or three to dissolve the sugar completely, once dissolved you can pretty much just leave it in a cool dark place until Xmas.
Decant - via muslin to remove 'bits' - into suitable containers and enjoy immediately. Some insane people talk about then leaving it thus contained to 'mature' for a further year, but, really, as if...