With regard to the erysimum, only give it a light trim l believe. You could try rooting the tips as cuttings. I know Bowles Mauve can get a bit leggy so it's best to propagate that by cuttings to replace it. As nutcutlet said, l don't know which variety you have though. I think the iberis is pruned the same way.
Cut them back to strong side-shoots, the lower the better to help reduce their normal tendency to grow straggly. Use some side-shoots to make cuttings, too, particularly the erysimum, as they only last a few years at best and get very untidy.
A trowel in the hand is worth a thousand lost under a bush.
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In the sticks near Peterborough
I think the iberis is pruned the same way.