Thanks DT ..... on the link attached (hopefully!!) it's shown on the second image down. It's described there are fried rice noodles, but I am sure there is another name for this crunchy white stuff - and yes, there is crunchin the water chestnuts which I also use but it's this garnish I am after x http://missklicious.blogspot.co.uk/2010/12/cream-cafe-bar-2-civic-canberra.html
Not questioning you Echo but my local Waitrose is one of the smaller branches and they stock the Mama brand of Vermicelli noodles. They are in amongst the World Foods aisle but not with the rest of the noodles. The are in a semi translucent packaging and sort of cube like in shape.
You'll find them easily in any Chinese/Thai/Japanese grocer too.