The Realex documentation is very poor and in certain places incorrect. For example, some of the XML spec in reality contradicts the documentation.

But I did find the support good, especially a person called Anne Kehoe.

However, we switched from using hosted WorldPay to remote Realex and it is worth the pain. People are able to pay for stuff in about a third of the time as previous. That probably says more about the hard it is to use hosted Worldpay though for end users.