Almost certainly pollen beetles. When the oil seed rape is over where they reproduce to plague proportions, they find their way to our gardens where they can become a real pest. They don't actually do any harm but they are unsightly and ruin the appearance of the flowers.
You could try spraying with water and washing up liquid, but with cut flowers they should fly towards the light away from the flowers if put in a dark place which gives you 'clean' flowers.

Thanks Betiefox, we have fields of oil seed rape very near us, I'll try your spray suggestion. x

I'm glad this was asked as my flowers are smothered in them, too! Atleast now I know they're harmless :o)

No please, do not use washing up liquid as a spray. It is not good for bees etc. and in any case it will not kill beetles.
Before using Liquid soap as an insecticide one ought to read this http://en.wikipedia.org/wiki/Triclosan.

It's ok Owdboggy, I wasn't planning on spraying. Don't really fancy spraying my flowers in washing up liquid, I'll save that for the dishes!

Good oh!