Thanks for replies

Have i think sorted it - the code from the JAM site didn't seem to do as required for some reason but now working. The override is fine doing it as i originally did in ../cherrry_zen/checkout_success.
Whether it was solely the code or the fact the shop is on a different domain to JAM i am not sure but seems to be working now and commission going to the right place so i think i will leave well alone!!

Thanks again

Of course it could all just be a case of famous last words.....