// change button html to this
<button class="btn btn-simple center-block" data-loading-text="Loading..." autocomplete="off" id="more-charity">Load More </button>


// javascript

                $('#more-charity').click(function (ev) {

                   var form = $('#charity-form');
                   var $container = $('#charity-result');
                   var $button= $(this).button('loading');
                    $.ajax({
                        type: "GET",
                        cache: false,
                        url: "http://localhost/simplygiving/data/charities.dta",
                        success: function (response) {
                          var $container = $('#charity-result');
                          newItems=$(response);
                          $container.append( newItems ).isotope( 'appended',newItems);
                          $button.button('reset');
                        }

                        });

                    ev.preventDefault();

                });