I wasn't aware, that it is different in moodle 1.9.
I just took a quick look at 1.9. You could try the following:
In moodle\enrol\manua.enrol.php there's in line 73:
notice_yesno(get_string('enrolmentconfirmation'), "enrol.php?id=$course->id&confirm=1&sesskey=".sesskey(),
"enrol.php?id=$course->id&cancel=1");
You coud try to replace that with:
redirect("enrol.php?id=$course->id&confirm=1&sesskey=".sesskey());
It's certainly not very sophisticated, but it might work...
(I have no moodle 1.9 installation where I could acutaly test it.)
Christoph