I have just found out how to hard code change the way virtuemart lists its payment methods:

Locate the file:

components/com_virtuemart/themes/default/templates/checkout/list_payment_methods.tpl.php

Locate the code:

$ps_payment_method->list_nocheck($payment_method_id,  false);
$ps_payment_method->list_bank($payment_method_id,  false)
$ps_payment_method->list_paypalrelated($payment_method_id,  false);

You can then copy and paste the lines in order to change the order of t payment method category list. Changes within the category can be done in the payment method options list!

Hope this helps! Took me ages to find!