Thanks for the replies, looking through our job system (pages of it!!) it looks like we've tried most things.
My thoughts are that it isn't ONIVF compliant or uses a proprietary version of, as Foscam (in some listings) claim it has ONVIF capabilities. I don't think we can change the login string on the NVR, also it looks like we have tried various software based tools where you can specify a string and I assume that didn't work either.
I'll look for a polite way to tell the customer he has been done, I get the feeling he paid a lot more than the £99 (still expensive for what you get!) price I've just googled.
Thanks again for the replies.