Can anyone identify these flowers?

Right - will do!

 

I've just checked a German forum and found that I. Balsamica can be invasive - but is presumably not as bad as other Impatiens variants. Here's a translation in answer to the question "Are there any Impatiens that don't propagate themselves?"

Hardly - they are simply too good at doing this! The Impatiens Glandulifera and I. Balfour multiply so well that they are already on the black list in Switzerland or the observation list for dangerous botanical species. You should not put these Impatiens in a place where they could spread into the environment. At other places in the garden spread out Impatiens rather where other kinds find no good living space. If you definitely want to prevent propagation, you need to pick off the flowers before the seeds ripen.