Your piece (like the others mentioned by Anne and Keith) has speckles of enamel that have been picked up off the marver block when a clear gather of glass has been rolled across the enamels scattered on that block. Quite possibly there are also random bubbles, but they are seperate from the colour, not surrounded by it. This is not the way Nazeing colour is laid into the glass.
Interestingly, having come back to the thread, I've realised that the shape of your vase is indeed one linked with Stevens and Williams. Not proof, but at least it gets us looking in a particular direction. Certainly I used the same logic with the all green pieces with bubbles that were at one time confused with Nazeing, and later I managed to find the proof in the S&W description books.