Thanks Ross,
Here is my final JQuery solution which others may find useful:
jQuery(document).ready(function($) {
$(".searchandfilter .datepicker:first").datepicker({
dateFormat: "dd/mm/yy",
onSelect: function(dateText, instance) {
date = $.datepicker.parseDate(instance.settings.dateFormat, dateText, instance.settings);
date.setMonth(date.getMonth() + 1);
$(".searchandfilter .datepicker:last").datepicker("setDate", date);
}
});
$(".searchandfilter .datepicker::nth-child(1)").datepicker({
dateFormat: "dd/mm/yy"
});
})
This pre-populates the End Date with a month later when the Start Date is populated.
Thanks.