Thank you very much Preslav,
I've implemented this and it works fine for the most part (I've seen some oddness where upon clicking the filter button the open animation happens and then the popup closes).
Also, if you filter on another column (e.g. set Ship City to filter on "reims") and if you go back to the Shipped Date field the customisation has been lost, I found another post where if you wrap the function body (as below) it works fine:
e.container.data(
"kendoPopup"
).bind(
"open"
, function () {
//code block for menu customisation
});