the dark blue are sloe berries, except they're very big and not as sour as normal so I suspect possibly a cross with bullace. the sweetest will be the brown ones - medlar (once bletted), but this lot ...
Sour fruits for cheese is a smart ancestral move. The acidity aids preservation and digestion, bypassing the need for heavy sugar. Excellent way to keep your gut microbiome thriving without the modern junk food trap.