You can harvest, flower, leaf and fruit.
The flower makes a tasty syrup that when added to sparkling water is quite a nice drink, the fruit can be made into jelly or relish, it is better to cook this fruit as raw may upset your stomach. The young leaves can be eaten as they are in the spring. They can be harvested later in the year but they are not nearly as nice.
One note, do not eat the seeds and be sure to get all the stems off the fruit before processing.
And as a hedge..... it looks pretty and no one is going to push their way easily through it.
Thank you, this is all good to know!