Norman:
It looks like a Prachen piece to me. Is there a recess in the bottom? Does it have lots of variously sized bubbles? Does the yellow have more green it than is shown in the picture? If yes, I'd go with Prachen. I've got one and it's not the shape shown in Mark Hill's book (and neither is yours), so we could a piece from the 'Karneval' range, on which Mark says "Flora' was based.
David