Chris - looking through Geoff. Timberlake's book, there are many ashtrays shown, and apparently many more that weren't, but nothing quite like yours. They did produce some larger pieces with an internal patterning (created by pulling) called 'lattice' effect - the pulling of the colour created a zig-zag effect, and bubbles were also included in a spiral. Might you have been thinking of this? It's about the only design that comes anywhere near your piece, although it definitely isn't the same.
From what I can see in the book, it appears that this orange/red in your ashtray is not a colour used by Nazeing.