hi susie,
soft comfrey is an introduced garden perennial.
common and tuberous are both native perenials, common being robust up to a metre high and coming in a range of colours from white, to pink and blue.
tuberous our other native is cream and smaller with a tuberous root.
both common and tuberous flower later than soft which flowers from april.
you need to remember its stature, colour and when it flowered, the name creeping is not one i know and is maybe a regional common name,
but if its cream flowered and fairly short, as it was in your garden, my bet would be soft.
gary
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