We had a thread on this a while back. Have a look on Google at Prunus
sericifera and see if that rings any bells.

Are you refering to Prunus cerasifera or cherry plum ??.

My fruit is a touch smaller in dia and is very deep mauve/purple, its
not red.

The best I can come up with is a Shropshire prune. but not knowing the
actual size I am not sure.