This is a wild cherry, Prunus padus. This species is common all over northern Europe. But it is quite problematic as bonsai. It hates to be wired, actually it hates to be a bonsai. Branches die without warning. Anyway, the nebari of tis one is very good.
It is the tree of my childhoodl. I used to sit in the wild cherry trees which smelled so strong when flowering. I brought home branches with flowers and my mother would throw them away immediatly because of the strong scent. She said 'they stink'. Well, such is life.