We are in North Shropshire too and no plums except for 1 Marjorie which was full of worms. We are hoping that this break in production will reduce the number of worms in future as it will take a while for the population to recover. No sloes either and very very few Damsons.
The trees also are going down for Winter very early, the leaves are getting very old and tired ( just like me).
I would not let the damaged plums you have go on to the heap though. They are a source of Brown rot for next year. Collect up fallen fruit and dispose of in the Compost bin or burn.

thanks for the responses guys. The apples on the small wall creeper were not so good either. But on the plus side loads of blackberries, raspberries and good old rhubarb.