I have finnaly solved the problem with a little help from a colleague. The problem was the adapter class I specified in the spring-ws config:
the second bean declaration I had should not be there: once I took this out it worked fine
<property name="marshaller" ref="xmlbeansMarshaller" />
<property name="unmarshaller" ref="xmlbeansMarshaller" />
I can't remember where I took the example from, but hopefully if anyone else does the same they will end up on this thread and get the answer quickly....