Another one where it would be better to wait until the flowers have finished, though then you would lose the berries.

Thanks Owdboggy will do

Personally would wait until autumn to prune.

You can prune immediately after they've flowered if they're something like Berberis darwinii. If they're deciduous ones such as Berberis thunbergii, these aren't grown for their flowers anyway, they're fairly insignificant, so you can prune them earlier if you want.

Thanks