Thanks Eng Swee,
I think my problem might be related to 2 things
1.) The 3rd party web service provides a WSDL without a fault message (https://services.postcodeanywhere.co.uk/CapturePlus/Interactive/Find/v2.10/wsdl.ws) . However, they send a standard soap fault message on error as shown in the original post. So far that seems indeed comply to the soap fault standard.
2.) They send (as far as I can see) HTTP 200, even on fault. However, I tried with a soupUI mockup service which sends HTTP 500 but with the same behavior.
To overcome 1.) I imported the W3C soap xsd (http://schemas.xmlsoap.org/soap/envelope/) as an external definition (type XSD) and refenced the "Fault" message within my inbound synchronous interface. However, this doesn't seem to do the trick
I don't know if 2.) is anything of an interest or if 200 or 500 should both be ok to catch application faults.
I also read about some people activating "do not use soap envelope" but this seems like a big backdraw, as normal response works fine
Many thanks
Cheers
Jens