Although some people won't agree, many trees and shrubs only have a limited life. It could be that your amalanchier knows this and has made an attempt to reproduce by flowering and setting some seed through its berries. Give it a good watering and a mulch and perhaps a light prune as you have nothing to lose.

Expected life span for these is over 60 years - any chance of a photograph or three, showing the trunk as well as the branches and upper parts?

There seems to be a lot of trees and shrubs in the UK losing their leaves early this year. Has there been a huge heat wave and drought this summer?

well we have had a sudden heatwave but it is cooling off now. but we also had a warm march and cold april.
I suspect its lack of water.

Tug; if Maurudi is in the South, we've had no rain at all for nearly a month, and prior to that, only a little on and off for about 4 days, none at all for a month before that, and we had temps of 30-35 degrees for five days in West London, with high uv. So in the south, that would be the most likely explanation

Sounds sadly likely. It sounds like this summer has been hard for you folks. Around here, we never rely on the rain for water, but our latest heat wave has been revealing the flaws in the mismanaged irrigation systems common to the Valley of the Sun.