Hi Humph. How far north are you that blackberries aren't ready?! or is this an effect of your exposed wind-tunnel garden?
Damsons, in my limited experience, can be used in most of the same ways as plums with a couple of caveats: 1. they are smaller and therefore fiddlier, making the de-stoning stage rather labour intensive, 2. They are high in pectin and acid (reference: 'Cooking Explained', Barbara Hammond, 2nd ed, 1974, with a library stamp in the front that my mother has obviously tried to obscure before handing it on to me...!), which means to each kg of fruit use 1.25 to 1.5kg of sugar, and when first stewing the fruit add 400-900ml water per kg.
Others in the high pectin group are cooking/crab-apples, black/red currants, green gooseberries. Plums are in the average bracket along with Apricots, Blackberries, Raspberries and Loganberries. Low pectin/acid group is Late season blackberries, Cherries, Pears, Strawberries. You need to add 1-2tbsps lemon juice or half to 1 tsp tartaric acid per kg to these before starting cooking. Or for apparently a shorter boiling time, retaining more of the flavour, use lemon juice plus half a bottle (per kg) of 'Certo' liquid pectin which is 2.99 in Lakeland or 2.29 in Tesco...
We've been spared this weather it seems. It has rained all morning - a sort of steady drizzle-plus. I did bring in a squash and some tomatoes last night but by the time i got out there it was dark. Must find my headtorch and keep it next to my wellies.
I am home sick today with sniffles, aches, sore throat, general ennui. Can't go outside (although am tempted to wrap up with scarf like it's winter...) but am loving the vivid wet colours of the garden that I can see from my kitchen extension - great thing about a small garden is you can see it all at once, it's like a stage set. Top of the list when I do get out there is to glypho that bindweed that's coming through the fence from next door...