Why am I getting problems with username & password for WP cron?
The problem was the single quotes around the path to cron.php, once I removed them it worked.  Also usr/bin/wget was incorrect, just needs wget. Here's the working crontab entry with output redirected for debugging.

wget -O - -q -t 1 http://example.org.uk/wp-content/plugins/civicrm/civicrm/bin/cron.php?name=Cronjob\&amp;pass=xxxxx\&amp;key=2c3b60639d70ba87f61e819cb2cd0e67 &gt; /home/example/www/wp-content/uploads/civicrm/ConfigAndLog/cronerrors.txt 2&gt;&amp;1