set the permittion of your upload folder, set the highest 0777 value, if its working then set lower and lower while its uploding your file. This setting could be different on different servers, you should ask the server vendor.
Notice that this error:
/home/pixelriteuk/public_html//uploads/Murray.JPG
it has double slash sign. Print the $_SERVER['DOCUMENT_ROOT'] to know how your document root variable looks like, if the last character is a slash, then do this:
change this line:
$uploadDir = $_SERVER['DOCUMENT_ROOT'] . '/uploads/';
into:
$uploadDir = $_SERVER['DOCUMENT_ROOT'] . 'uploads/';
While you're testing set to inactive the header(location) redirection. On a live system its suggested to hide the error reporting!