We've got a damson tree too and it's fruit are nearly ripe. The other plum, an Oulins gage didn't do anything but it was only planted last year and looks healthy so maybe next year. It is supposed to be a lot more reliable and heavier cropping than the "old" greengage type.
Staying with trees. The pear tree has also done well as have most of the apples. Scrumptious is ready and the Bramley is about there. Our "unknown" is a bit of a disappointment in that for some reason the only section I can get to easily has not fruited. I'll still be able to pick some though and as usual will be juicing what we have, probably mid to late September.