This grower is sure of this plant identification.
Myrtle euphorbia, Blue spurge
Euphorbia myrisinites (Myrtle euphorbia). The foliage is grey-green, with sulphur yellow flowers which can grow to 4ins in diameter. This is an evergreen and has a trailing habit which will make it an ideal container plant, with grey-green foliage.
They are fully hardy to frost tender, min 5-15C, and will grow well in sun or partial shade with moist but well drained soil.
Container, border, window-box.