Thanks for the great extension! I have noticed a tiny bug in this plugin, in the file "ds-sagepay-direct.php on line 692, it reads:
if ($this->description) echo wpautop(wptexturize($this->description));
"echo" shouldnt be used here, as the function outputs the data automatically. using echo results in this appearing twice on the Thank You page once the order is complete.
Could you remove "echo" so that it just appears once?