The quotes you are using aren't consistent! Both your opening and closing quotes need to be the same.
Try this:
$playdotcom = file_get_contents("http://www.play.com/Search.html?searchstring=".$getdata['getlist_item']."&searchsource=0&searchtype=r2alldvd");
$amazoncouk = file_get_contents("http://www.amazon.co.uk/gp/search?search-alias=dvd&keywords=".$getdata['getlist_item']);
As it were ".$getdata[getlist_item]." was considered part of the string as you never closed the single quote string you initiated.