The attached code provides a simple, albeit naive approach to adding PartnerLinkType elements to the outgoing WSDL document generated by the WSDLBuilder. The approach would work with extending any WSDLBuilder (not just the JAXBWSDLBuilder shown), but because there aren't really any clearly defined interfaces or attachment points for doing this I was unable to do-so without modifying core X-Xfire code, which I don't want to do for licencing reasons!
I hope someone finds this useful and can embed it in the core XFire code as PartnerLinkType is a requirement for a Web Service to be consumed by a BPEL defined process, so should be becoming more of a requirement as time goes on. Even more useful would be a generic attachment point for modifying the WSDL, if there was a clearly defined interface I would have been able to decorate an existing WSDLBuilder class, but my attempt to extend WSDLBuilder failed miserably
Many thanks to Dean who did all the work on this code, I just pulled his utility classes into place