That seems to have done it. Thanks again guys.
Edit:
Actually does not appear to have worked. Visually it work but functionally it does not. Tom, if I add what you suggested nothing on the site is clickable. So it works visually but not functionally. Sorry.
Edit 2:
I think I might have got it. If I do the following it seems to work:
#page {
position: relative;
z-index: 0;
}
.after-header-search {
position: -webkit-sticky;
position: sticky;
top: 55px;
z-index: 1;
}