Found these over on bagworth heath. I'm speculating that they are tall melilot as the flowers look right with lobes and keel being the same length so discounting the other melilot. Problem is the leaves aren't showing any signs of the jagged edges. My mothers dubious on the basis of the leaves and suggests Genista tinctoria but then the flowers doesn't look quite right and when closed they curve upwards whereas these when closed curve downwards like the melilots
I think you are in the right area, Ian, but I agree that the leaves don't look quite right. The leaves appear trifoliate, which would rule out Dyer's Greenweed and most yellow Fabaceae apart from melilots and medicks. The key in Stace depends on details of leaves/stipules, rather than flowers, so I can't tell from the photo.
Sue