Hi Dan
Have you already tried to create your WSDL file? If not check this:
How to consume B1if Web Services with HTTPS by DotNet?
Once you got it you can go the element: 'wsdl:portType' and in the 'name' attribute is your URL. In child elements 'wsdl:operation' you can check what are the names of your web methods.
In general this URL is similar to this one: ipostep_vP.001sap0011.in_WCSX_com.sap.b1i.vplatform.runtime_INB_WS_CALL_SYNC_XPT_INB_WS_CALL_SYNC_XPT.ipo_proc
Please mind that '001sap0011' is the system Id (from SLD) which is assigned to your scenario as a sender system.
btw
I think that you need to create WSDL file in order to be able to test your scenario using SOAP UI - at least that's what I do.
Kind regards,
Radek