OK solved this for anyone else the reponse url is ../before_process.php
Hoever I now have an issue that during testing all cards are ok except visa cards which return the error:
Realex errorIPAYMENT_ERROR_MESSAGE
Hello
I have installed the realex module avaiulabe at http://addons.oscommerce.com/info/4217 but I cannot see what the referral/response urls are supposed to be? any help appreciated