SOAPUI. Accessing a basic authentication webservice through companies web proxy

Hi.  I'm on SOAPUI v5.2.1.

I need to call an internet exposed service from inside my companies network.  To get out to the internet I need to go through the companies web proxy.  Windows domain\user credentials allow this.  The target WebService expects basic authentication credentials.

I configure Preferences->Proxy Settings (pointing at the proxies IP, on port 80, specifying by domain\user\password)

In the HTTP header I see a Authorization : Basic : elements added with a base64 encoded string.

I can hit the target endpoint - but get a noat authorised error (not suprisingly).

NOW:

I add the basic authentication details to my request -> Authorization Basic, username/password...

I now get an Error getting response;java.lang.NullPointerException...

I don't see anything in the requests http headers to do with authorization at all.

SO:

Any tips for setting up access to a basic auth protected http web service when accessing via a web proxy that also needs to be authenticated to?

Thanks

Jamie