Oops - Found the issue which is different to other examples I have seen on Google. For some reason I had commented out this block in my website (WCF host) web.config
<system.serviceModel>
<behaviors>
<serviceBehaviors>
<behavior name="">
<serviceMetadata httpGetEnabled="true" />
<serviceDebug includeExceptionDetailInFaults="false" />
</behavior>
</serviceBehaviors>
</behaviors>
<serviceHostingEnvironment multipleSiteBindingsEnabled="true" />
Putting that back in and I'm back in business.