Sorbus, probably S. aucuparia.

Yes, Sorbus aucuparia. Aka Mountain Ash or Rowan. But it’s not a true ash. Sorbus was one of the suggestions I gave for your berries.

eta Yes, it is a common tree here.

Thank you for your replies! I wonder if either of them could be a different species of Sorbus. The berries were not all collected from the same park and I notice that the ones gathered under the tree I uploaded have larger and darker coloured berries. Unless it is due to normal species variability...Here's a photo from the two types of berries for comparison.

There are many species, hybrids and cultivars of Sorbus grown here. But the tree in the photo looks like S aucuparia. ‘Joseph Rock’ is the commonest cultivar of that species grown here but since it’s a native there will be a lot of the straight species about. The difference in the berries could be due to their stage of decomposition or to variability within or between species/cultivars. You can’t tell from some shrivelled fruit.