That big green cabbagey thing is indeed an opium poppy (Papaver somniferum.) The other one to the left is a different kind of poppy, maybe common poppy (Papaver rhoeas.)
A trowel in the hand is worth a thousand lost under a bush.
Opium poppies vary a lot in flower colour and form. Some of the double flowers are incredible but even the singles are pretty. The dried seed heads usually last over the winter and look fantastic with a bit of frost on them. The foliage does get a bit messy as the season goes on but unsightly leaves can be easily pulled off.
A trowel in the hand is worth a thousand lost under a bush.
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Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.